Democrats reeling from a devastating election face a daunting task: the 2018 Senate map.

It favors Republicans in a big way. The GOP will be defending just eight seats, while Democrats must fight for 23 — plus another two held by independents who caucus with Democrats.

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What’s worse is the fact that many of the seats they must defend are in states won by Republican Donald Trump Donald John TrumpTrump says he doesn't think he could've done more to stop virus spread Conservative activist Lauren Witzke wins GOP Senate primary in Delaware Trump defends claim coronavirus will disappear, citing 'herd mentality' MORE.

Midterm elections for sitting presidents are historically challenging. Democrats in the Senate are hoping to find some political momentum for 2018 given the difficult playing ground.

Here are 10 Senate seats that could flip, in alphabetical order:

Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE (D-Fla.)

Democrats came into 2016 bullish about the Sunshine State.

But Republican incumbent Marco Rubio Marco Antonio RubioThe Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump, Biden couldn't be more different on climate change Congress should support independent oversight of federal prisons Senate panel seeks documents in probe of DHS whistleblower complaint MORE’s decision to run for reelection cleared the muddled field and, ultimately, a surge in rural Republican voters outpaced Democrats’ gains in cities and with Hispanics. When the dust settled, Trump won by 1 percentage point, while Rubio held on to his seat by 8 points.

Nelson, a three-term senator, is a well-known commodity in Florida, having held public office there since 1972. And he starts with a net 14-point approval rating, according to an October poll from Public Policy Polling.

Possible challengers could include term-limited Gov. Rick Scott (R), a Trump ally, or any of the politicians who eyed the seat in 2016, including outgoing GOP Reps. David Jolly or Ron DeSantis.

Millionaire Carlos Beruff and Lt. Gov. Carlos Lopez-Cantera, both 2016 candidates, could also jump in. But the two are Scott allies, so it’s unlikely either would challenge the governor should he decide to run.

Joe Donnelly Joseph (Joe) Simon DonnellyEx-Sen. Joe Donnelly endorses Biden Lobbying world 70 former senators propose bipartisan caucus for incumbents MORE (D-Ind.)

No state’s Senate race changed more in 2016 than Indiana’s. Republicans started the cycle looking likely to keep control of outgoing Sen. Dan Coats Daniel (Dan) Ray CoatsThe Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump, Biden renew push for Latino support Former Intel chief had 'deep suspicions' that Putin 'had something on Trump': book Overnight Defense: Woodward book causes new firestorm | Book says Trump lashed out at generals, told Woodward about secret weapons system | US withdrawing thousands of troops from Iraq MORE’s seat with Democratic Rep. Barron Hill in the race. Then it seemed destined to go Democratic once Hill dropped out and former Sen. Evan Bayh jumped in.

But a flurry of damaging stories and revelations stunted Bayh’s comeback, giving Rep. Todd Young Todd Christopher YoungWhy the US should rely more on strategy, not sanctions Davis: The Hall of Shame for GOP senators who remain silent on Donald Trump Republicans dismiss Trump proposal to delay election MORE a 10-point win behind Trump’s 19-point victory.

Donnelly seemed to have an uphill battle against Sen. Richard Lugar (R) in 2012, until the incumbent was toppled by former Indiana Treasurer Richard Mourdock.

Look for a much tighter race now, with potential GOP candidates such as Reps. Luke Messer, Susan Brooks Susan Wiant BrooksHouse Democrats' campaign arm reserves .6M in ads in competitive districts Stefanik credits Trump for spike in GOP women running for office DCCC reserves new ad buys in competitive districts, adds new members to 'Red to Blue' program MORE or Marlin Stutzman, who ran in the primary this past spring, in the mix.

Claire McCaskill Claire Conner McCaskillDemocratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally Missouri county issues travel advisory for Lake of the Ozarks after Memorial Day parties MORE (D-Mo.)

Democrats are fresh off of a tight loss challenging Republican Sen. Roy Blunt Roy Dean BluntGOP senators say coronavirus deal dead until after election Pessimism grows as hopes fade for coronavirus deal CDC says asymptomatic people don't need testing, draws criticism from experts MORE’s reelection and now have to pivot to defending one of their own. Democrat Jason Kander fell to Blunt by 3 points, while Trump won the state by 19 points.

McCaskill has won tough races before — she defeated incumbent Republican Sen. Jim Talent for her seat in 2008 and dispatched Rep. Todd Akin in 2012, a race that had been considered close until Akin’s infamous comment about “legitimate rape.”

Republicans will likely eye the red-state seat as a major pickup opportunity, potentially by one of the state’s six GOP lawmakers.

Jon Tester Jonathan (Jon) TesterPence seeks to boost Daines in critical Montana Senate race This World Suicide Prevention Day, let's recommit to protecting the lives of our veterans Filibuster fight looms if Democrats retake Senate MORE (D-Mont.)

Tester steered the Democratic Senatorial Campaign Committee in 2016, so he’s led the party through its share of tough races. And winning as a Democrat in Montana is no easy feat.

Trump won the presidential vote by 21 points in Montana, but Gov. Steve Bullock (D) tapped into the state’s bipartisan leanings with his own 4-point win.

GOP Rep. Ryan Zinke, the state’s only congressman, is seen as best positioned for a potential Tester challenge.

Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R-Nev.)

Nevada was one of the shining lights for Democrats up and down the ticket in 2016 — Clinton held the state by 2 points, the same margin that former state Attorney General Catherine Cortez Masto defeated Republican Rep. Joe Heck by to win the open Senate seat.

That’ll give Democrats confidence coming into one of their few strong pickup opportunities of 2018.

Look for the scramble to start right back up, with names like Rep. Dina Titus and retiring Sen. Harry Reid Harry Mason ReidBottom line Filibuster fight looms if Democrats retake Senate Biden unites Democrats — for now MORE’s son Rory leading the first round of speculation.

Heidi Heitkamp Mary (Heidi) Kathryn HeitkampCentrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents Susan Collins set to play pivotal role in impeachment drama MORE (D-N.D.)

North Dakota is another ruby-red state coming off a Republican blowout in 2016. Trump won by 36 points, Sen. John Hoeven John Henry HoevenDavis: The Hall of Shame for GOP senators who remain silent on Donald Trump Bottom line Bipartisan senators seek funding for pork producers forced to euthanize livestock MORE won reelection by 62 points, and Republican Gov.-elect Doug Burgum won by 58 points.

Rep. Kevin Cramer (R), the state’s only congressman, could entertain a bid against one of the Senate’s 21 women.

Sherrod Brown Sherrod Campbell BrownEmboldened Democrats haggle over 2021 agenda Hillicon Valley: Russia 'amplifying' concerns around mail-in voting to undermine election | Facebook and Twitter take steps to limit Trump remarks on voting | Facebook to block political ads ahead of election Top Democrats press Trump to sanction Russian individuals over 2020 election interference efforts MORE (D-Ohio)

Brown’s populist streak has won him favor in Ohio for more than two decades, including two terms in the Senate, helping him win reelection in 2012 by 6 points.

But Ohio took a sharp turn in the GOP’s direction in 2016, with Trump winning by 8 points, a larger margin than each of the past five presidential elections there. And Sen. Rob Portman Robert (Rob) Jones PortmanRomney undecided on authorizing subpoenas for GOP Obama-era probes Congress needs to prioritize government digital service delivery House passes B bill to boost Postal Service MORE won by 21 points over his Democratic challenger, former Gov. Ted Strickland.

A term-limited Gov. John Kasich (R) could look to jump back to Congress, or state Treasurer Josh Mandel could look for a rematch against Brown, depending on who decides to run to replace Kasich.

Bob Casey Robert (Bob) Patrick CaseyCatholic group launches .7M campaign against Biden targeting swing-state voters GOP senator to quarantine after coronavirus exposure Court documents show Postal Service removed 711 mail-sorting machines this year MORE (D-Pa.)

The Casey name has been in Pennsylvania politics for about a half-century, beginning with Casey’s father, who started in the state Senate in 1963 before stints as the auditor general and governor.

Casey has won big even in the tight state — he defeated incumbent GOP Sen. Rick Santorum by 18 points in 2006 and won reelection by 9 points in 2012.

This year, GOP Sen. Pat Toomey won reelection by 2 points, bucking all the polls, and the electorate only stands to become more favorable for Republicans in an off year.

Potential candidates could include two early Trump backers in Congress, Reps. Lou Barletta Louis (Lou) James BarlettaBottom Line Ex-GOP congressman to lead group to protect Italian products from tariffs Head of Pennsylvania GOP resigns over alleged explicit texts MORE and Tom Marino, or others such as Rep. Pat Meehan. State Senate Majority Leader Jake Corman is another who could consider a bid, but many are in a holding pattern until Gov. Tom Wolf (D) decides whether he’ll seek reelection.

Joe Manchin Joseph (Joe) ManchinOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency House Democrats tee up vote on climate-focused energy bill next week MORE (D-W.Va.)

Manchin’s decision to run for reelection boosted the hopes of Democrats looking to hold the deep-red state.

Trump won the state by 42 points, but the Mountain State bucked the idea of voting straight ticket, electing Democratic coal executive Jim Justice to the governor’s mansion with a 7-point margin.

Republican state Attorney General Patrick Morrisey could consider a bid, as could GOP Reps. David McKinley David Bennett McKinleyEnergy secretary says pipeline setbacks pose national security issue MLB, Congress play hardball in fight over minor leagues Koch campaign touts bipartisan group behind ag labor immigration bill MORE, Alex Mooney or Evan Jenkins.

Tammy Baldwin Tammy Suzanne BaldwinKeep teachers in the classroom Cher raised million for Biden campaign at LGBTQ-themed fundraiser Democrats seek balance in backing protests, condemning violence MORE (D-Wis.)

The Wisconsin Republican infrastructure in the state helped Gov. Scott Walker win three elections in six years, including during the 2012 election that saw wins by both Baldwin and President Obama.

Trump’s 1-point victory there, as well as Johnson’s comeback 3-point victory, gives Republicans hope to build on those margins with a midterm electorate.

Walker is likely to run for reelection, but his lieutenant governor, Rebecca Kleefisch, could decide to go national. Rep. Sean Duffy Sean DuffyCNN's Ana Navarro to host Biden roundtable on making 'Trump a one-term president' Bottom line McCarthy blasts Pelosi's comments on Trump's weight MORE is another name mentioned as a potential Senate contender.