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The 10 Most Vulnerable Senators in 2018: Heidi Heitkamp Moves to Top Spot

North Dakota Democrat tops Roll Call’s latest list of endangered Senate incumbents

Sen. Heidi Heitkamp, D-N.D., tops the list of most vulnerable Senate incumbents. (Tom Williams/CQ Roll Call file photo)
Sen. Heidi Heitkamp, D-N.D., tops the list of most vulnerable Senate incumbents. (Tom Williams/CQ Roll Call file photo)

Democrats continue to dominate the latest list of the most vulnerable Senate incumbents two months out from Election Day, with North Dakota Sen. Heidi Heitkamp moving into the top spot.

Heitkamp displaces Nevada Sen. Dean Heller, who nevertheless remains the most vulnerable incumbent on the Republican side and the only GOP senator running in a state Hillary Clinton won in 2016.

The Democrats battling for re-election in states that backed President Donald Trump remain among the most vulnerable senators.

[The 10 Most Vulnerable House Members in 2018 List Remains All-Republican]

Florida Sen. Bill Nelson moved up a spot ahead of West Virginia’s Joe Manchin III, even though Trump won West Virginia by 42 points. Manchin’s opponent, state Attorney General Patrick Morrisey, had to contend with a costly primary, while Nelson’s opponent, Gov. Rick Scott, has showed he’s willing to spend millions on his race.

As always, these lists are compiled after consultation with strategists from both sides of the aisle and the race ratings from Inside Elections with Nathan L. Gonzales. We look solely at vulnerable incumbents and do not include open seats that are likely to flip.

1. Sen. Heidi Heitkamp, D-N.D.

Heitkamp moves to the top spot due to a combination of polling, a tough challenger and her state’s partisan shift. She still might be able to bring together a coalition of voters to prevail, but North Dakota has shifted further right since she won a first Senate term by less than 1 point in 2012. While she has her own brand in the state, so does her opponent, GOP Rep. Kevin Cramer, who represents the entire state as its at-large House member. Cramer lags behind Heitkamp in fundraising, but the dynamics are still tough for North Dakota’s last remaining statewide Democrat. Race Rating: Tilts Republican

  Watch: ‘North Dakota Nice’ Takes a Backseat in Senate Race

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2. Sen. Dean Heller, R-Nev.

Heller is still in a tenuous position in a swing state and facing a challenger who’s raking in lots of campaign cash and using the money to hit the airwaves. Democratic Rep. Jacky Rosen has spent nearly $5.6 million through June 30, while Heller has shelled out $5.3 million and he has a cash-on-hand advantage. An environment favoring Democrats could help Rosen unseat the incumbent, who still has to contend with his back and forth over health care legislation last year. Race Rating: Toss-up

3. Sen. Claire McCaskill, D-Mo.

The two-term senator is facing a tough race against GOP state Attorney General Josh Hawley. Operatives on both sides expect this to be one of the closest races in the country, with McCaskill on defense in a state Trump carried by 19 points. Hawley has latched on to the Supreme Court vacancy to fire up his base, while McCaskill has the dual task of courting moderates and independent voters while significantly boosting Democratic turnout, especially among African-American voters. Race Rating: Toss-up

4. Sen. Joe Donnelly, D-Ind.

The first-term senator moves down a spot, but he still faces daunting odds in a deep-red state. His GOP opponent’s vulnerabilities from his business background, though, could help mitigate what had emerged as an early attack on Donnelly over outsourcing. Former state Rep. Mike Braun spent more than $6 million of his own money winning the three-way GOP primary in May, but so far hasn’t shown the same willingness to dip into his own coffers for the general election. Donnelly has been touting his working relationship with Trump, even as the president comes to the state to campaign with Braun. Race Rating: Toss-up

5. Sen. Bill Nelson, D-Fla.

Despite Florida being a more Democratic state than most on this list, the third-term senator moves up a spot. He’s facing his biggest challenge yet against Scott. As a sitting office holder flush with money, Scott’s had a heavy paid and earned media presence. He’s been airing television ads since April, while Nelson released his first spot last week. Outside groups have been boosting Nelson on the airwaves, but keeping up with Scott’s millions in such an expensive media market will be tough. Race Rating: Toss-up

6. Sen. Joe Manchin III, D-W.Va.

No one on this list is running for re-election in a bigger Trump state than Manchin. But the former governor has actually moved down a spot in the months since the May GOP primary. Democrats spent money to help state Attorney General Patrick Morrisey become the nominee, banking on his ties to the pharmaceutical industry and New Jersey roots not going over well in the Mountain State. Morrisey is using his record as attorney general to paint a contrast to Manchin’s time in Washington, but Democrats have been hitting back at Morrisey for backing a lawsuit against the 2010 health care law. Race Rating: Tilts Democratic

7. Sen. Jon Tester, D-Mont.

Tester remains in the same place he was four months ago. The National Republican Senatorial Committee recently started spending in the state and released a poll showing Republican Matt Rosendale ahead, though within the margin of error. Democrats are seeing much stronger numbers for Tester here, while Democrats and some Republicans see Rosendale as a flawed candidate to take on a lifelong farmer. Still, Trump remains popular in Montana, and if Rosendale gets enough help from outside groups to nationalize the race, Tester — a former DSCC chairman who’s never won more than 50 percent of the vote in his Senate races — could be in trouble. Race Rating: Tilts Democratic

8. Sen. Tammy Baldwin, D-Wis.

Baldwin now knows her Republican challenger, state Sen. Leah Vukmir, who has a billionaire backer. Outside money has already poured into the state, which Trump won by less than 1 point in 2016. Republicans have been successful in recent midterm years in Wisconsin, but a national environment favoring Democrats could help Baldwin this time. She also starts the race with a sizable financial advantage after Vukmir was forced to spend in the competitive August primary. Race Rating: Leans Democratic

9. Sen. Sherrod Brown, D-Ohio

The two-term senator may be running for re-election in a state that’s trending away from Democrats, but he remains the favored candidate against GOP Rep. James B. Renacci, a wealthy congressman and former registered lobbyist. Renacci has plenty of his own resources to bring to the race but national Republicans remain frustrated that he’s not tapping those coffers and not raising or spending enough money to make this race more competitive. Race Rating: Likely Democratic

10. Sen. Bob Casey, D-Pa.

Casey remains among the least vulnerable Democratic incumbents running in states Trump won. He faces GOP Rep. Lou Barletta, whose lackluster fundraising has frustrated some Republicans and kept him from making the race more competitive. Trump has traveled to the state to campaign for Barletta, but the president’s involvement might not be as helpful here as in other states. Race Rating: Likely Democratic


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