The Senate battlefield is finally taking shape.
A rash of Republicans taking steps toward Senate campaigns in recent weeks has jolted races in states such as Missouri, Montana, and Pennsylvania that for months lacked top-tier challengers. Still, several recruitment holes remain, and who fills them will have significant implications on the Senate’s party division in the next Congress.
Even a wave probably wouldn’t put the GOP's grip on Senate control in serious jeopardy thanks to a favorable map and the Republican vice president's tie-breaking vote. Conversely, it’s unclear if the GOP can capitalize on a cycle with a plethora of Democratic targets while running into what has historically been midterm headwinds for the party in the White House.
President Trump’s approval rating dropped to new lows this month and continues to weigh on the Senate landscape. Meanwhile, Democratic senators in states that backed him have raised strong sums in anticipation of difficult reelections.
Democrats dominate this list of the seats most likely to flip party control, just as they did in Hotline’s previous Senate rankings in March. But there is one fewer Democratic seat this time.
Arizona's move up to No. 9 bumped Wisconsin to 10 and edged out Pennsylvania, where Democratic Sen. Robert Casey may face Republican Rep. Lou Barletta. That race could reemerge on this list at a later date depending in part on how the races above it shake out.
1. Missouri—Sen. Claire McCaskill (D)
State Attorney General Josh Hawley’s expected challenge gives Republicans one of their strongest recruits in an increasingly conservative state where Trump remains popular. Hawley could face a primary even with Republican Rep. Ann Wagner out of the race, but GOP leaders are confident that he will emerge as their nominee. McCaskill, who has won the seat twice, has ramped up her fundraising operation and is talking up her role as a watchdog in the Senate as she actively courts the state’s rural communities. But she is unlikely to enjoy the perfect storm that aided her in 2012, when she faced the deeply controversial Todd Akin.
2. Nevada—Sen. Dean Heller (R)
As the only Republican up in a state that Hillary Clinton won, Heller’s highly competitive reelection became even more difficult after Danny Tarkanian declared a primary challenge. The first-term senator will now be forced to spend resources trying to shore up a base that still views him skeptically after he criticized Trump during the presidential primary and came out against a health-care-replacement plan. Democrats, meanwhile, are seizing on his shifting health care positions—he supported the so-called “skinny” repeal bill—and are eagerly lining up behind freshman Rep. Jacky Rosen. The party is cautiously optimistic that she will not face a primary with Rep. Dina Titus, who is considering a campaign.
3. Indiana—Sen. Joe Donnelly (D)
The fast-escalating primary between Reps. Luke Messer and Todd Rokita is expected to turn into one of the nastiest and most hard-fought on the map. But Republicans still stand to benefit from the fundamentals of a state that has moved right and supported Trump by 19 points. Donnelly could benefit from his moderate image, reflected in his willingness to work with the White House on some issues and support for Supreme Court Justice Neil Gorsuch. Still, his path remains difficult as he prepares to face a GOP nominee much tougher than his flawed 2012 opponent, Richard Mourdock.
4. West Virginia—Sen. Joe Manchin (D)
It’s getting lonely at the top for Manchin. Gov. Jim Justice’s high-profile switch to the Republican Party this month gave the GOP an opening to question why the senator hasn’t done the same. The National Republican Senatorial Committee quickly launched a digital ad highlighting Manchin’s support for Hillary Clinton and labeling him “out of touch,” which promises to be a recurring theme in the campaign to oust perhaps the only Democrat who could survive a statewide federal election here at this point. On Manchin’s side is the GOP primary between state Attorney General Patrick Morrisey and Rep. Evan Jenkins, which is reminiscent of the Republican race in Indiana.
5. North Dakota—Sen. Heidi Heitkamp (D)
Heitkamp still doesn’t have a Republican challenger in a state that gave Trump his fourth-largest victory and led all others in presidential-margin shift toward the GOP from 2012 to 2016. That, along with Heitkamp’s $3 million raised over the first six months of the year, her strong approval rating, and a map stacked with turnover possibility, means Heitkamp can barely crack the top-five most-vulnerable senators. The wait continues for Rep. Kevin Cramer to announce his intentions, as well as a list of potential contenders that includes state Sen. Tom Campbell, oil-field consulting company founder Kathy Neset, and state Rep. Rick Becker.
6. Florida—Sen. Bill Nelson (D)
This ranking banks on Gov. Rick Scott entering the race, as expected. He'd start off with near-universal name recognition and significant resources, two critical assets in the large and expensive state. Scott, a wealthy businessman, has spent millions to get elected before and would likely do so again in a bid against the three-term incumbent. Given those advantages, Scott has made clear that he is in no rush to enter the race and for now is freezing the GOP field. Nelson has never before faced an opponent as strongly financed and formidable as Scott, but he already had $5 million on hand after the second quarter in preparation for the fight.
7. Montana—Sen. Jon Tester (D)
Tester’s vulnerability drops with every formidable Republican who takes a pass on the race. First it was Rep. Ryan Zinke, who joined the Trump administration. Then came state Attorney General Tim Fox in early June. But among the several Republicans in the race now is state Auditor Matt Rosendale, who finished third in the 2014 House primary. Like Tester, Rosendale sports a flat top and served as a leader in the legislature. But unlike the incumbent, Rosendale isn’t a Montana native, and he’s already taking friendly fire for his Maryland roots. Tester starts with a $4.7 million cash-on-hand advantage.
8. Ohio—Sen. Sherrod Brown (D)
Josh Mandel had more than $3 million in the bank by the end of June, but he has also received months of bad press over the taxpayer-funded TV ads he ran from the state treasurer’s office. Rep. Pat Tiberi opted against running but now, in investment banker Michael Gibbons, Mandel has a wealthy primary opponent with a professional consulting team and supportive super PAC. Gibbons is already on TV and threatens to keep Mandel from a second shot against Brown, who has twice as much cash as Mandel but must defend his seat in a state that Trump carried by 8 points.
9. Arizona—Sen. Jeff Flake (R)
The potential for a bloody Republican primary and for Democratic Rep. Kyrsten Sinema to run pushed this seat into the top 10, nudging out Pennsylvania. Both states were carried narrowly by Trump and the competitiveness of both races relies on a House member’s candidacy. But the $300,000 initial investment by GOP mega-donor Robert Mercer in a super PAC supporting former state Sen. Kelli Ward indicates that Trump could have more than a passing interest in unseating the incumbent. And while Mercer spent more than twice as much aiding Ward’s unsuccessful challenge to Sen. John McCain last year, Flake’s vocal criticism of Trump could turn off enough of the president’s supporters to make it close.
10. Wisconsin—Sen. Tammy Baldwin (D)
The GOP primary to face Baldwin is hazier than ever, though Republicans hope to avoid a replay of their nasty intraparty fight in 2012. Marine veteran Kevin Nicholson is the only official GOP candidate so far but is unlikely to clear the field: Several other Republicans, including 2012 candidate Eric Hovde and state Sen. Leah Vukmir, are openly weighing bids. Republicans are convinced that the first-term incumbent is too liberal in a state with a recent history of GOP success in midterm years. Democrats have already deployed field organizers in the state, as Baldwin promotes her work on issues including “Made in America” proposals.