There are 468 races being fought in the midterm congressional elections Tuesday, but the big picture depends on hardly more than a dozen.

That’s because the central question is, and has been for more than a year, whether Republicans can retake the Senate and thus control both chambers of Congress. And that will depend on the outcome of the 15 races the Washington Examiner is focusing on in its election cheat sheet.

This is the third election cycle in which Democrats have had to defend more Senate seats than the GOP, but Republicans blew their opportunities to capture Capitol Hill entirely in 2010 and 2012.

This time around, their candidates look more electable and have committed fewer unforced errors.

States that were thought to be out of play have expanded the map of battlegrounds: In Kansas, Republican Sen. Pat Roberts has been obliged to fight hard against an unexpectedly strong challenge from Greg Orman, an independent backed by Democrats. In Iowa, Republican Joni Ernst has taken advantage of early missteps by Democratic Rep. Bruce Braley, who was the early favorite in the race.

Voter frustrations with Obamacare have not dominated the election, as some pundits predicted. Instead, these midterms have been defined by dissatisfaction with the president himself, and with those Democrats seen as his close adherents.

Republicans have pummeled Democratic incumbents in advertisements and in campaign speeches for the votes they have cast to pass President Obama’s policies. Those vulnerable Democrats have tried to steer the conversation away from fraught national issues and have shunned their own leader for fear of taint.

Persuading voters has never been more expensive. Candidates, party committees and outside groups have poured hundreds of millions of dollars into midterm races. More than $100 million has been spent in North Carolina alone, ranking that race among the most expensive Senate contest ever. Not all races will be decided on Tuesday. In Louisiana and Georgia, contests will probably extend into runoffs. In the latter race, between Republican David Perdue and Democrat Michelle Nunn, the outcome appears to be a tossup.

We have arranged the 15 states in our cheat sheet in order of closeness, with the first, North Carolina, being the hardest to predict.

1. North Carolina

Kay Hagan vs. Thom Tillis

2008: Hagan 53 percent; Elizabeth Dole 44 percent

2012: Romney 50 percent; Obama 48 percent

The fight in North Carolina has focused on an unpopular legislative body in which voters have lost confidence.

No, not Congress. The state legislature.

Democratic Sen. Kay Hagan, one of the most vulnerable incumbents in this midterm election, foresaw a narrow path to victory by turning the campaign’s focus away from the shortcomings of President Obama and Congress to those of the North Carolina General Assembly and her Republican challenger, House Speaker Thom Tillis.

A noisy, lengthy summer session by the state legislature lent itself to this strategy, and Tillis emerged from the wreckage in August at a disadvantage. His standing was further eroded by controversial cuts in education spending, where Hagan concentrated her fire.

But recent national events have turned the race on its head. Tillis has invoked the Republican trifecta of ISIS, Ebola and border security to raise questions about the president’s competency in office and to tie Hagan to his unpopular policies.

After holding a strong lead over Tillis in public polling in September, Hagan’s margin has shrunk throughout October, leaving the race a genuine tossup.

Early in-person voting in North Carolina began Oct. 23. In the meantime, both parties have scrambled to spend millions more on the key race, one of the most expensive in the nation. – Rebecca Berg

2. Iowa

Bruce Braley vs. Joni Ernst

2008: Tom Harkin, 63 percent; Christopher Reed, 37 percent

2012: Obama 52 percent; Romney 46 percent

Nobody expected the Iowa Senate race to be competitive, even in a good midterm year for Democrats. Now the race to replace retiring Democratic Sen. Tom Harkin could end up being one of the closest contests of the 2014 election cycle.

Iowa State Sen. Joni Ernst won the Republican June primary by uniting all factions of the GOP coalition. The Tea Party supports her, as does the GOP establishment. She surged into contention on the strength of her plainspoken likability and background as an Iraq War veteran, as well as President Obama’s low approval rating and early missteps by Democratic Rep. Bruce Braley.

But Braley has proved resilient. In midsummer Ernst jumped out to a lead in public opinion polls; by early September Braley had caught her. By mid-September Ernst was back up — and although she maintains a small lead, Braley is nipping at her heels. Braley is hammering Ernst for her conservative positions on social issues, particularly her opposition to most abortions.

Ernst has relentlessly tied Braley to Obama, charging that the congressman has voted with the president 96 percent of the time, and has criticized him for supporting Obamacare. The Ernst campaign also has continued to highlight remarks Braley made in a closed-door setting in which he ridiculed Sen. Chuck Grassley, R-Iowa, as a farmer who never went to law school. The race could boil down to how the campaigns perform with early voters. Iowans are used to voting before Election Day. Both camps made a hard push this year to encourage their supporters, and likely supporters who don’t usually vote in midterm elections, to vote early.

Democrats traditionally far outpace Republicans in rounding up early and absentee votes, but the GOP believes it has made marked improvements there. – David M. Drucker

3. Georgia

Michelle Nunn vs. David Perdue

2008 (runoff): Saxby Chambliss 57 percent; Jim Martin 43 percent

2012: Romney 53 percent; Obama 45 percent

For the next few days, Georgia will be on everyone’s mind.

The state has become a source of thinly veiled dread for national Republicans as nominee David Perdue has struggled to defend himself from attacks over corporate outsourcing and has seen his lead vaporize in recent polls. Most prognosticators expect the Republican to pull off a win — this is Georgia, after all — but it won’t be pretty.

The RealClearPolitics polling average gives Perdue a slight lead over Democratic nominee Michelle Nunn. Some election watchers say underpolling of African-Americans means polls are overestimating the Republican’s fragile advantage. The state’s demographics have changed substantially in recent years — Georgia has become less and less white — which is why it’s in Democrats’ cross hairs in the first place. If Republicans can’t keep the seat this year, it will be enormously difficult for them to take it back in 2020. The fact that the contest is so close in a year that is supposed to feature a wave of wins for Republicans means Georgia could be a liability for the GOP in the next presidential election.

Overhanging all of this is the lingering specter of a Senate runoff. Unless one of the candidates gets more than 50 percent of the vote Tuesday, there will be another round of voting on Jan. 6. This wouldn’t be unprecedented; Senate races went to a runoff in 2008 and 1992. A runoff would probably favor Perdue, but it would be an unfortunate reminder to national Republicans that things aren’t as peachy as they once were in the Peach State. – Betsy Woodruff

4. Kansas

Pat Roberts vs. Greg Orman

2008: Roberts 60.1 percent; Jim Slattery 36.5 percent

2012: Romney, 59.6 percent; Obama, 38 percent

Roberts should be coasting to re-election in this ruby red state just as he did in 2008. But a bruising primary against Tea Party Republican Milton Wolf and questions about whether Roberts maintains a residence in Kansas set the table for an unlikely general election challenge.

Enter Greg Orman, a wealthy businessman running as an independent. Orman clearly benefited from Democratic moves to push their Senate nominee, Chad Taylor, off the ballot, and he has capitalized on the shenanigans. The telegenic, energetic 45-year-old presents a stark contrast to the 78-year-old Roberts, and he sprinted to an early lead over his Republican opponent. Orman attacked both major political parties as being part of the problem in Washington, and he vowed to make “solving problems” a priority and to put Kansas first. The message had legs.

But Roberts fought back. He overhauled his campaign team, raised sorely needed funds and attacked Orman as a “liberal Democrat.”

Orman’s past associations with and contributions to major Democratic figures helped Roberts make his case. (Orman briefly ran for Senate as a Democrat in 2008.) Orman further helped Roberts by refusing to take stands on key positions or confirm which party he would caucus with if elected to the Senate, allowing Roberts to frame the campaign as a referendum on President Obama and Democratic Senate Majority Leader Harry Reid. That message, combined with millions of dollars in outside help from GOP allies, helped to turn this race around for Roberts.

The contest remains competitive, but most Kansas GOP insiders expect Roberts to pull it out on Election Day. – David M. Drucker

5. Colorado

Mark Udall vs. Cory Gardner

2008: Udall 52.8 percent; Bob Schaffer, 42.5 percent

2012: Obama 51.5 percent; Romney 46 percent

Mark Udall coasted to his first Senate term over a lackluster GOP opponent six years ago in what was perhaps the best Democratic year in a generation. Not so this year.

Republican Rep. Cory Gardner has not only made Colorado competitive, he led in many polls down the stretch and appeared to stymie the Democrats’ greatest perceived asset in this race: the party’s advantage among female voters. Udall has vigorously prosecuted a “war on women” campaign against Gardner, who opposes abortion rights and at one time supported an initiative that would have granted the rights of “personhood” to fetuses at conception.

This strategy helped Sen. Michael Bennet stave off a Republican challenge in 2010, a Republican wave year. The problem for Udall is that it just isn’t working this time. For his near-singular focus on women’s reproductive issues, Udall has been nicknamed “Mark Uterus.” He still leads Gardner among female voters. But the Republican’s decision to run on a broader array of concerns has paid dividends with voters, who have warmed to his upbeat, unflappable demeanor. Gardner has no doubt been boosted by his change of heart on the personhood issue and policy proposal to make birth control available to women over the counter.

Colorado is a swing state that has lately tilted toward Democrats. The party has basically run the table there in state and federal elections since 2006, with the exception of losing two congressional races in the Republican wave year of 2010. But that could change this year. Democrats are counting on a strong ground game to make up any deficit Udall might have in the public opinion polls, and believe Colorado’s move to all-mail voting could give them an edge. Of note: Bennet is chairman of the Democratic Senatorial Campaign Committee, the group charged with holding onto control of the Senate for his party. – David M. Drucker

6. Louisiana

Mary Landrieu vs. Bill Cassidy and Rob Maness

2008: Landrieu 52.1 percent; John Kennedy Neely 45.7 percent

2012: Romney 58 percent; Obama 41 percent

It’s a safe bet that nobody is happy with how the Louisiana Senate race is panning out.

Incumbent Democratic Sen. Mary Landrieu has a history of pulling off nail-biter wins, but to truly put this contest to bed she has to get more than 50 percent of the vote on Election Day. That’s unlikely. And thanks to Tea Party-backed candidate Rob Maness, Republican candidate Rep. Bill Cassidy is also unlikely to break that mark. So the election is probably headed to a Dec. 6 runoff. That means a few more weeks of work for beleaguered campaign staff and, potentially, no final answer in November as to who controls the Senate.

Thus far, none of the candidates has drawn remarkable poll numbers. RealClearPolitics’ polling average gives Landrieu 38 percent, Cassidy 33.8, and Maness 9 percent, as of Oct. 31. Maness hasn’t generated enough positive buzz to boost his fundraising or raise his name recognition, but he still pulls enough votes away from Cassidy to almost guarantee a runoff. In head-to-head polls between Cassidy and Landrieu, the Republican leads by an average of 5.3 percentage points.

The contest is very pricey — together, the candidates and outside groups have spent a whopping $25 million. While that pales in comparison to North Carolina’s Senate race, where spending has topped $62 million, it’s still a good chunk of change. – Betsy Woodruff

7. Kentucky

Mitch McConnell vs. Alison Lundergan Grimes

2008: McConnell, 53 percent; Bruce Lunsford 47 percent

2012: Romney 60.5 percent; Obama 37.8 percent

At first blush, it would appear that McConnell shouldn’t have a problem winning re-election in a state that went Republican for president by more than 22 points. But the Bluegrass State is more complicated than that.

Kentucky still regularly puts Democrats in charge of state government. The governor’s mansion and the legislature are both controlled by the Democratic Party. That openness to Democratic rule — combined with McConnell’s low job-approval rating, a tough challenge from the right in the GOP primary and the target placed on his back by national Democrats — meant the Senate’s top Republican was almost assuredly headed for a tough re-election battle.

Grimes, the 35-year-old sitting secretary of state and scion of a powerful Kentucky Democratic family, didn’t disappoint. She has kept the race close on the strength of strong fundraising and the support she received from Democrats across the country given the fact that she is running against the would-be Republican majority leader of the U.S. Senate. But in the campaign’s final days, McConnell has had the edge.

Obama’s dismal approval ratings outweighed McConnell’s, as illustrated by Grimes’ refusal to say whether she voted for him for president. McConnell wasn’t perfect on the stump, particularly when discussing the Affordable Care Act, a program that is unpopular in Kentucky but has spawned Kynect, the state’s Obamacare online exchange for purchasing health insurance, which is popular.

But Grimes was noticeably unpolished for a candidate running for Senate. She often appeared unprepared to answer questions on issues of the day that she might be expected to deal with as a senator, and even her fans thought she was too scripted and stiff.

Tactically and strategically, McConnell did almost everything right. He was scheduled to outspend Grimes on television ads by a significant margin during the final two weeks of the campaign. If he maintains the edge and Republicans flip a net six Democrat-held Senate seats, McConnell will succeed Sen. Harry Reid, D-Nev., as majority leader in January. – David M. Drucker

8. New Hampshire

Jeanne Shaheen vs. Scott Brown

2008: Shaheen 52 percent; John Sununu 45 percent

2012: Obama 52 percent; Romney 46 percent

New Hampshire wasn’t supposed to be a horse race.

When former Massachusetts Sen. Scott Brown announced he would be leaving Massachusetts and moving north so he could challenge Democratic incumbent Sen. Jeanne Shaheen, he drew guffaws, naysayers and snark. Despite the arguments to be made against Brown’s candidacy — this is the carpetbagger who just got walloped by Occupy Wall Street darling Elizabeth Warren, after all — the Granite State has national Republicans keeping their fingers crossed.

The RealClearPolitics polling average gives Shaheen a slight over Brown, and just one recent public poll shows her with a lead outside the margin of error. Shaheen’s left-leaning compatriots are taking notice; Daily Kos recently moved its race rating from likely D to leans D. “Both parties and their allies are spending big here, and the polls still point to a Shaheen win,” wrote election watchers Jeff Singer and David Nir, “but a win for ‘bqhatevwr’ isn’t as improbable as it used to look.”

In Brown’s favor: According to the Boston Globe, President Obama got an anemic 38 percent approval rating from likely voters in one September poll. In Shaheen’s: Warren recently visited New Hampshire to campaign for the incumbent, perhaps excited by the prospect of working to defeat Brown a second time. – Betsy Woodruff

9. Alaska

Mark Begich vs. Dan Sullivan

2008: Begich 48 percent; Ted Stevens 47 percent

2012: Romney 55 percent; Obama 41 percent

The Last Frontier state could be Democrats’ final frontier in their bid to keep control of the Senate.

And the race between Sen. Mark Begich, the Democratic incumbent, and Republican Dan Sullivan is up for grabs.

Begich is among the most vulnerable Democratic incumbents, but strategists from both parties have been impressed by his re-election strategy, which focused early on local issues and worked to define Sullivan as an outsider who does not understand Alaska.

Begich has touted himself as a reflection of “True Alaska,” a nod to his roots in the state. Sullivan has called Begich “pure Washington.”

Begich has been swimming against a strong anti-Obama tide — and Sullivan, an active commanding officer in the Marine Corps and a former assistant secretary of state, has relentlessly tied Begich to the president and his policies.

Alaska is a fiercely independent and unique state that can be remarkably unpredictable. Public polling is scattershot and in some elections has widely missed the mark.

Begich hopes to turn out robust support from Alaska’s rural areas, home to many Native Alaskans who often do not vote. That unprecedented effort to get out the vote will be supplemented by 128 new early voting locations.

Sullivan, meanwhile, will draw his support largely from Alaska’s cities — including Anchorage, where Begich was mayor before winning election to the Senate six years ago. – Rebecca Berg

10. Arkansas

Mark Pryor vs. Tom Cotton

2008: Pryor 80 percent; Rebekah Kennedy (Green Party) 20 percent

2012: Romney 61 percent; Obama 37 percent

Sen. Mark Pryor has had to contend with perhaps the most inhospitable political climate of any Democratic incumbent this year.

The electorate in Arkansas has gradually become more Republican since Pryor’s last competitive race in 2002, leaving him in a state uniquely hostile to President Obama. Meanwhile, the specter of low turnout in a midterm election year, which tends to favor Republicans, demands that Pryor turn out an unusually large number of Democratic voters.

On top of all this, Pryor has faced a spirited challenge from Republican Rep. Tom Cotton, whose Ivy League credentials and military service adorn a sparkling resume.

Pryor has pushed back by portraying first-term lawmaker Cotton as “entitled” and inexperienced, and Pryor has tapped his father, the former senator and governor, to emphasize his Arkansas roots. But Cotton, like Republican candidates in other states, has been successful at tying Pryor to the president and his policies in a state where Obama’s approval barely tops 30 percent, according to a recent NBC News/Marist poll.

Public polling has favored Cotton since September, and he has led Pryor by an average of 5 points during the final month of the election.

Early voting began Oct. 20. – Rebecca Berg

11. Michigan

Terri Lynn Land vs. Gary Peters

2008: Carl Levin 63 percent; Jack Hoogendyk 33 percent

2012: Obama 54 percent; Romney 45 percent

For Republican nominee Terri Lynn Land, this race has gone from bleak to bleaker.

Apart from an upbeat Oct. 8 sampling from Republican pollster Wenzel Strategies, Land has lagged significantly. Her campaign has drawn criticism for avoiding media and making awkward public appearances. It is still technically possible she could pull off a win — Land’s campaign is well funded, and some observers say polls have been oversampling Democrats — but Democrats don’t seem to be sweating this contest. The NRSC, formerly the National Republican Senatorial Committee, canceled TV ads it had reserved for the last two weeks of campaigning.

That said, Land’s campaign has leveled blistering criticism at Michigan media and Democrats for attacks it calls sexist and demeaning. State Democrats criticized Land on Twitter for mentioning she was a mom multiple times in an interview. Republicans rallied behind Michigan’s former secretary of state, with New Hampshire Sen. Kelly Ayotte joining a conference call to denounce the attacks.

Still, the likely question on election night will be whether pollsters overestimated Rep. Gary Peters’ margin of victory. – Betsy Woodruff

12. Virginia

Mark Warner vs. Ed Gillespie

2008: Warner 65 percent; Jim Gilmore 34 percent

2012: Obama 51 percent; Romney 47 percent

Republicans have found little to celebrate in Virginia over the past few election cycles, but they hope to break Democrats’ winning streak this time.

A win by former Republican National Committee Chairman Ed Gillespie would be a very big surprise given his unimpressive poll numbers. But incumbent Democratic Sen. Mark Warner has had a bit of an October surprise in the form of accusations that he discussed offering a former state senator’s daughter a federal judgeship in exchange for staying in the state Senate. Gillespie put out a statewide TV ad about that one.

Also worth noting: Polls of Virginia have been squirrelly of late. Most of the polling of the 2013 gubernatorial race showed Democrat Terry McAuliffe with a much bigger lead than the slim margin of victory that materialized for him on Election Day. Though he defeated Republican Attorney General Ken Cuccinelli by 3 points, some argued that better polling could have given Cuccinelli a boost in courting donors and potentially changed the outcome of that race. And, of course, there’s the notoriously awful primary polling in Virginia’s 7th Congressional District, where college professor and political neophyte Dave Brat defeated House Majority Leader Eric Cantor in an upset that sent shockwaves through American politics. – Betsy Woodruff

13. Minnesota

Al Franken vs. Mike McFadden

2008: Franken 42 percent; Norm Coleman 42 percent

2012: Obama 53 percent; Romney 45 percent

The Minnesota race features an incumbent who spent his first term trying to focus on the state versus a challenger determined to tie him to Washington and President Obama.

After winning office by just 312 votes in 2008 to become the Democrats’ 60th vote in the Senate, former comedian Al Franken realized just how precarious his position was. He spent the next six years bolstering his Minnesota presence, shunning national reporters and avoiding the limelight despite his background as an entertainer. But that wasn’t enough, as his Republican challenger, the 50-year-old former investment banker Mike McFadden, has sought to portray him as the manifestation of Washington partisanship and Obama’s favorite senator. At every possible opportunity, McFadden has reminded voters that Franken has voted with Obama 97 percent of the time.

Despite voters’ dissatisfaction with the president, Minnesota may be too blue for a strategy like McFadden’s to turn the tide. Minnesota has not voted for a GOP presidential candidate since 1972. Franken opened up a double-digit lead early, presenting a challenge for McFadden, who is new to politics and struggles with name recognition. Franken also has significantly outraised McFadden, drawing in far more money from outside the state as little Republican PAC money is showing up for McFadden. Early absentee and mail-in ballots were mostly from voters who had also been registered for the 2010 midterms and greatly favor Democrats. – Joseph Lawler

14. Oklahoma

James Lankford vs. Connie Johnson

2008: Jim Inhofe 57 percent; Andrew Rice 39 percent

2012: Obama 33 percent; Romney 67 percent

This race isn’t exactly a nail-biter. Spoiler alert: Lankford walks away with it.

Like Michigan’s Senate race, the most interesting thing about Oklahoma’s contest might be the margin of victory. Incumbent Republican Sen. Tom Coburn won 71 percent of the general election vote in 2010. Inhofe took 57 percent in 2008, and Coburn won 53 percent in 2004. Is Oklahoma getting redder? Or could it be lagging (far) behind perennially red states such as Texas and Georgia that are trending purple? And how do Oklahoma voters feel about gingers in general?

The most interesting part of this race was the Republican primary, which state Rep. T.W. Shannon — backed by former Alaska Gov. Sarah Palin, Texas Sen. Ted Cruz, Utah Sen. Mike Lee and the Senate Conservatives Fund — lost quite badly to Lankford. There don’t appear to be any burned bridges between the two primary contenders, but the biggest losers in Oklahoma this cycle are the conservatives who expended political capital in support of Shannon. – Betsy Woodruff

15. Oregon

Jeff Merkley vs. Monica Wehby

2008: Merkley 49 percent; Smith 46 percent

2012: Obama 54 percent; Romney 42 percent

Oregon was always going to be a long shot for Republicans.

They thought a gift had been handed to GOP candidate Monica Wehby when Oregon’s state healthcare website, which received $300 million in federal grants, got off to a disastrous start, temporarily hobbling incumbent Democratic Sen. Jeff Merkley. Republicans quickly dumped cash into the race to maximize the damage. But the race in the solid blue state has been basically ignored, having drawn just $2.3 million in outside spending, nearly $2 million of which was intended to boost Wehby, according to OpenSecrets.org.

Wehby has tried to portray Merkley as a lawmaker who carries President Obama’s agenda. But in Oregon, the man the New Republic called “a liberal lion with no roar” has a double-digit lead in most polls and will likely be giving a victory speech Tuesday night. He has focused his campaign largely on painting Wehby as too far right for Oregon and by mimicking Democrats’ national strategy of tying his opponent to the billionaire industrialist Koch brothers. Wehby wasn’t helped by a plagiarism scandal in September over allegations that she lifted her economic and healthcare policy proposals from Sen. Rob Portman, R-Ohio, and GOP policy shop Crossroads GPS. – Zack Colman

House Races

Election night will be all about the Senate, and understandably so. But a number of House contests also deserve a passing glance. Here’s a handful to keep an eye on:

Massachusetts 6: Democrat Seth Moulton beat incumbent John Tierney in the primary and now faces Republican Richard Tisei, the former state Senate minority leader looking to make GOP history by becoming the first openly gay member of his party elected to Congress. Democrats are bullish about Moulton. Republicans are bullish about Tisei. It’s interesting.

California 52: Another openly gay Republican candidate, Carl DeMaio, is facing incumbent Democrat Rep. Scott Peters in a district that Obama won by 6 points in 2012. Sexual harassment allegations and a plagiarism scandal have dogged DeMaio’s campaign, but the race is far from over.

Nebraska 2: Incumbent Rep. Lee Terry is slightly favored to beat Democratic challenger Brad Ashford, but it isn’t a done deal. If Lee wins, his margin of victory could indicate the down-ballot influence of Republican Senate nominee Ben Sasse.

Virginia 10: Republican state Del. Barbara Comstock faces Democratic Fairfax County Supervisor John Foust in a tight fight for retiring Rep. Frank Wolf’s seat. The Democratic Congressional Campaign Committee recently canceled a $2.8 million TV ad buy, and Comstock outraised Foust in the third quarter. So things look good for her. But it’s a district with a growing Hispanic population and it could be tough for Republicans to flip back if Foust snags a win.

West Virginia 3: Democratic Rep. Nick Rahall has been in national Republican cross hairs for what seems an eternity, and the GOP is proud of the challenger it recruited to face him. State Sen. Evan Jenkins, who has hit Rahall hard for his record on energy, left the Democratic Party to join the GOP so he could challenge Rahall. Good move? We’ll find out in a little bit. – Rebecca Berg