Republicans’ razor-thin three-seat majority in the Senate will be among the biggest fights during the 2020 election cycle, as Democrats look to not only win the White House but also gain full control of Congress.

Part of the reason this is such a big opportunity for Democrats is that Republicans will have to defend 22 seats in 2020 (many were first elected 2014 — a very strong year for Republicans) meaning Democrats are on offense. They are up in just 12 states.

Democrats do have certain factors playing in their favor. Trump’s low approval rating could be a drag on Republicans’ reelection bids, helping some Democrats ride to victory. After all, Trump is polling on net at -13 in Colorado, -15 in Maine, and -7 in Arizona — the places where Democrats have their best shots — according to Morning Consult.

But even with all that going for them, the path to a majority is still tenuous.

“What makes this map very deceiving was in 2018, Democrats had to defend five seats in states Trump won by 19 points or more,” said Jennifer Duffy, a Senate expert at the nonpartisan Cook Political Report. “In this case, there’s no Republican sitting in a state that Clinton won by more than 5.”

Just three Republican seats seem truly competitive, as far as the Cook Political Report is concerned: Colorado, Arizona, and Maine. The rest is a sea of red, including one seat Democrats have to defend in ultraconservative Alabama.

If Democrats manage to retake the White House, a Senate majority stands between them and the ability to pursue any real legislative agenda and, crucially, the ability to confirm nominees to the Supreme Court and other important positions. Without the Senate, some of Democrats’ most ambitious ideas will remain pipe dreams.

Democrats’ biggest targets: flipping Colorado, Arizona, and Maine, and keeping Alabama blue

Colorado is Democrats’ best shot

Who is the Republican? Incumbent Sen. Cory Gardner.

Who are the Democrats? Former governor John Hickenlooper, who dropped his flailing presidential bid to pursue the Senate nomination, is the biggest name. But there are 11 other candidates in the race including: former state Sen. Michael Johnston, former Colorado House Speaker Andrew Romanoff, former Colorado House Majority Leader Alice Madden, former Ambassador Dan Baer, a climate activist Diana Bray, community activist Lorena Garcia, University of Colorado’s Colorado Springs professor and pastor Stephany Rose Spaulding, former U.S. Attorney John Walsh, Denver-based immigration advocate Michelle Ferrigno Warren, Colorado state Rep. Angela Williams and scientist Trish Zornio.

What’s the playing field?

Colorado is by far Democrats biggest target. The demographics are shaping up for Democrats in Colorado; the state’s Latino population has changed the political tide in the state, as have young voters, and Trump’s popularity in Colorado has tanked ever since he took office. Meanwhile, Gardner, who still has to play to a Republican base that likes Trump, has done little to distance himself from the president. He supports Trump’s national emergency for the border wall. He cemented his reputation a party man, and in 2018 successfully chaired the National Senate Republican Committee, the official campaign arm for Senate Republicans.

Six years ago, Gardner was a rising star in the Republican Party, ousting Democratic senator Mark Udall. He campaigned as a fair-minded Republican in a red wave election cycle. A Democrat did win statewide in Colorado that year, however: Hickenlooper kept his governorship. Hickenlooper’s decision to ditch his presidential ambitions for the Senate race has already gotten national attention — and an endorsement from the official campaign arm for Senate Democrats. But the other candidates — many more progressive, and women of color, haven’t cleared the field for him.

In Arizona, appointed Republican senator Martha McSally has to run a race she lost in 2018

Who are the Republicans? sitting Sen. Martha McSally, who was appointed to serve out the late Sen. John McCain’s term. Daniel McCarthy, a Phoenix-area businessman, is also running for the seat.

Who is the Democrat? Mark Kelly, a retired astronaut, military veteran and gun control advocate

What’s the playing field?

McSally lost her Senate race to Democrat Kyrsten Sinema in 2018 and got to be a senator anyways, appointed to serve out McCain’s term. Now she has to run again in a special election — and actually win — to keep her seat. In other words, Arizona Republicans have to prove that their losing candidate is actually a winner. McSally is a well-known entity in Arizona, after Republicans pulled out all the stops for her just last year. The problem is, even with high name recognition, she’s still not that popular — which is why McCarthy has thrown his hat into the ring. National Republicans are backing McSally, but you can never count out an unexpected Republican primary challenger.

Kelly is the husband to former House representative Gabby Giffords, who was shot in the head in 2011 at a local event in Tuscon, Arizona; together they run the group Americans for Responsible Solutions, a non-profit and Super PAC dedicated to preventing gun violence. The race is within reach for Democrats; Kelly has been raising more money than McSally, and despite being lesser-known is well liked.

Alabama’s Democratic Sen. Doug Jones has to keep his seat

Who are the Republicans? Former US Attorney General and senator Jeff Sessions announced he’s running for his old seat. He’s joining a huge Republican field. Rep. Bradley Byrne, a top Republican recruit, is running. Roy Moore, the controversial state judge who lost the race to Jones in 2017, is running again. Alabama’s current Secretary of State John Merrill, Alabama House Rep. Arnold Mooney, former televangelist Stanley Adair, and former Auburn University football coach Tommy Tuberville are also in the race.

Who is the Democrat? Incumbent Sen. Doug Jones.

What’s the playing field?

Jones won an unbelievable Democratic victory in the Alabama Senate special election to replace former Attorney General Jeff Sessions in December of 2017. Jones defeated Moore, who was accused of multiple instances of inappropriate sexual behavior with teenage girls — one as young as 14 — when he was in 30s. Moore also questioned whether Muslims should be allowed to serve in Congress, and stated homosexuality should be illegal.

Now, Moore is back in the race, along with another huge name in Alabama politics: Jeff Sessions. Sessions recently announced he’d run for his old Senate seat, becoming the favorite to win because of his name recognition, money, and clout in the state. But first he has to get through a crowded primary.

No matter what, the dynamics will be tough for Jones. Alabama’s electorate heavily sides with Republicans; the state voted for Trump by over 30 points in 2016. Still, recent Morning Consult polling found Jones’s net approval actually went up by 4 points from spring to fall 2019, with 41 percent of voters who approve of him and 36 percent who disapprove. Jones’ chief media strategist Joe Trippi told Vox after the race that “key to us having a chance was to detribalize the politics of the state. If Alabama was reacting to the tribal politics of our times, there was no way for us to win.” To win, they will have to do that again — but this time in presidential election cycle.

Maine: Republican Sen. Susan Collins is underwater

Who is the Republican? Sen. Susan Collins

Who are the Democrats? Maine House Speaker Sara Gideon, who was endorsed by the Democratic Senatorial Campaign Committee. Progressive activist Betsy Sweet and attorney Bre Kidman are also running as Democrats.

What’s the playing field?

Collins has never had a reason to be nervous about her re-election; she’s the quintessential moderate Maine Republican and has sailed to victory numerous times. But Collins is already facing attacks from both sides: Republicans are still incensed with her pivotal no vote helping defeat the 2017 GOP bill to repeal the Affordable Care Act and Democrats are furious with her yes votes on the GOP tax bill and confirmation of Supreme Court Justice Brett Kavanaugh.

Plus, Maine voted for Hillary Clinton in 2016, and Trump’s approval rating there is at a dismal 37 percent.

Democrats are on the offensive. But the rest of the map looks tough.

Both of Georgia’s Senate seat will be up in 2020

Who are the Republicans? Sen. David Perdue is running for re-election. Sen. Johnny Isakson is retiring and we don’t know who Gov. Brian Kemp will appoint, yet.

Who are the Democrats? Declared candidates for Perdue’s seat include, Jon Ossoff, who ran and lost a close House race in a 2017 special election; Columbus, Georgia Mayor Teresa Tomlinson; auto executive Sarah Riggs Amico; high school teacher Akhenaten Amun; former Georgia House candidate Marckeith DeJesus and mayor of Clarkston Ted Terry are declared.

What’s the playing field?

Stacey Abrams dashed the hopes of national Democrats when she declared she wouldn’t run for Georgia’s Senate seat in 2020 after managing to run a tight race against Kemp last year. After Isakson’s news, she reiterated that she wouldn’t be jumping in the race, instead sticking to her work on voting rights.

But Democrats still see some hope in Georgia especially after Rep. Lucy McBath defeated Republican Karen Handel in the state’s 6th Congressional District. The president’s approval rating in the state is still above water, though it has dropped significantly since he took office.

North Carolina is still a swing state

Who are the Republicans? Sitting Sen. Republican Sen. Thom Tillis is up for reelection. He has a primary challenger, retired business executive Garland Tucker III.

Who are the Democrats? State Sen. Erica Smith; Trevor Fuller, a former county commissioner chair; Durham businessman Steven Williams; and veteran and former state lawmaker Cal Cunningham, who ran for Senate in 2010 and lost.

What’s the playing field?

North Carolina Democrats saw a rare 2016 victory in North Carolina when Democratic Gov. Roy Cooper won the same year Trump clinched the state. Now, Tillis is in a tough race, starting with the GOP primary. Tillis has been dogged by attacks from conservatives questioning his allegiance to the president after he spearheaded an effort to shield special counsel Robert Mueller from Trump’s interference. There are already signs he is taking his primary seriously.

Democrats will be watching the outcome of the primary closely.

Iowa is a long shot but Trump’s unpopular there

Who is the Republican? Sen. Joni Ernst

Who are the Democrats? Businesswoman Theresa Greenfield has staked out early support, military veteran Michael Franken, lawyer Kimberly Graham, business owner Eddie Mauro.

What’s the playing field?

Ernst, a conservative combat veteran — and the first woman Iowa has sent to Congress — will be extremely tough for Democrats to beat in 2020. The first-term senator and combat veteran saw her approval rating rise at the beginning of the year to 57 percent in a February Des Moines Register/Mediacom Iowa Poll. That’s a 10 percent rise from fall 2018. Meanwhile, the president’s net approval in the state is underwater. Ernst votes with Trump 90 percent of the time.

Iowans are mad about Trump’s trade war with China and while the president remains popular with state Republicans, Democrats managed to flip two conservative congressional seats in 2018. If Democrats are more fired up than Republicans in 2020, Ernst could have a tougher race. But national Democrats still don’t have a particularly well-known challenger in the race.

Kansas has an open Senate seat and Democrats did have big wins there in 2018

Who are the Republicans? Trump-ally and former secretary of state Kris Kobach, Kansas State Treasurer Jacob LaTurner, former Kansas City Chiefs football player Dave Lindstrom, Republican commentator Bryan Pruitt, president of the Kansas Senate Susan Wagle, and Topeka resident Gabriel Mark Robles.

Who are the Democrats? Former U.S. Attorney Barry Grissom, former Kansas congresswoman Nancy Boyda.

What’s the playing field?

The 2020 retirement of longtime Sen. Pat Roberts has already triggered a big field of candidates vying to replace him. Kansas Democrats have a reason to be optimistic; they had a very good year in 2018 with Democrat Laura Kelly beating controversial former Kansas secretary of state and Trump ally Kris Kobach in the governor’s race, freshman Rep. Sharice Davids (D), an openly gay Native American woman, won Kansas’ Third Congressional District, and Democrat Paul Davis came extremely close in the state’s Second Congressional District.

Notably, the official campaign arm for Senate Republicans blasted Kobach’s announcement.

“Just last year Kris Kobach ran and lost to a Democrat,” NRSC spokeswoman Joanna Rodriguez said in a statement to the Washington Post. “Now, he wants to do the same and simultaneously put President Trump’s presidency and Senate majority at risk. We know Kansans won’t let that happen and we look forward to watching the Republican candidate they do choose win next fall.”

Years of steep tax cuts and underfunding schools spurred a backlash against Republicans. But there’s still not a standout Democratic candidate in the race.

Democrats got really close to winning Texas in 2018. They couldn’t do it.

Who is the Republican? Republican Sen. John Cornyn

Who are the Democrats? Democrats are banking on M.J. Hegar, an air force veteran who narrowly lost to incumbent Rep. John Carter (R-TX) in 2018. But it’s a wide field. Other candidates include Cristina Tzintzún Ramirez, the founder and executive director of Jolt, a group that mobilizes young Latino voters. Poor People’s Campaign activist Sema Hernandez, State Sen. Royce West, former Houston state Rep. Chris Bell, Houston Councilwoman Amanda Edwards, and Rev. Michael Cooper are also in the race.

What’s the playing field?

Beto O’Rourke made Democrats believe winning statewide in Texas was possible, when he lost to Ted Cruz by just two points in 2018 — the closest statewide race in the state since the 1970s. But if there was a lesson learned from 2018, it was that winning Texas needs someone like Beto O’Rourke, the charismatic, grassroots campaigner that not only won the hearts of Texas liberals but liberals across the country.

There’s a Senate race in Texas in 2020; Republican Sen. John Cornyn, who’s less popular in the state than Cruz, is up for reelection. The problem is Beto O’Rourke has moved on. He’s running for President and has pretty firmly shut the door on running for Senate again. As is Julian Castro, the former Obama cabinet official who has long been talked about as the man who could bring a blue wave to Texas.

Montana has a term-limited Democratic governor who is running for president

Who is the Republican? Republican incumbent Sen. Steve Daines.

Who are the Democrats? Helena Mayor Wilmot Collins, Montana’s first black mayor, a Liberian refugee and a veteran.

What’s the playing field?

Montana is a very red state. Theoretically it could be in Democrats’ grasp if they run the perfect candidate against Daines. The only problem is their perfect candidate — term-limited Gov. Steve Bullock — is running for president instead. Bullock is the most popular statewide official in Montana, and has a good track record of passing bipartisan bills like infrastructure, Medicaid expansion, and aggressive campaign finance laws cracking down on dark money in state elections. All of these things make him national Democrats’ top choice to take on Daines. Still, Bullock has been pretty clear: no Senate race — not now, not ever. His frustration is he’s a former state executive, and doesn’t feel like transitioning over to a body that is not doing much.

A defensive state that could still be very expensive

Trump’s former campaign manager could run in New Hampshire

Who is the Democrat? Sen. Jeanne Shaheen, New Hampshire’s first female governor and senior senator who has been serving in the Senate since 2009.

Who are the Republicans? Former speaker of the New Hampshire House Bill O’Brien and retired Brig. Gen. Don Bolduc are the two most well-known Republican candidates, but Trump’s former campaign manager Corey Lewandowski has been hinting for months he’s interested to run.

What’s the playing field?

New Hampshire is a well-known independent state, but it has been getting bluer in recent years. Shaheen is a longtime politician in the state who is fairly uncontroversial and popular. However, this race could get extremely expensive if Lewandowski runs. Trump, Lewandowski’s former boss, is very popular with New Hampshire Republicans, but he is underwater with New Hampshire’s all-important constituency of Independent voters. Shaheen will more than likely hang onto her seat even if Lewandowski runs, but his name could boost the race’s profile, and the amount of money spent.