With most primaries completed, a Supreme Court nomination on the table, and fewer than 100 days to go before the midterm elections, Republicans remain favored to hang on to or even grow their Senate majority.
Establishment forces have successfully recruited competent nominees to face well-funded Democratic incumbents in states Donald Trump carried just two years ago. But with generic polling and special elections indicating a shift in the national mood back toward the minority party, there’s a small chance Democrats can flip two seats and reelect all of their vulnerable incumbents.
The chamber’s two leaders, Republican Mitch McConnell and Democrat Chuck Schumer, their multimillion-dollar super PACs, and the national party committees all appear aligned on where Senate control will be decided. Those are reflected in our latest ranking of the most vulnerable seats, listed in order of most likely to flip.
Notably missing are three Midwestern states that Trump carried—Ohio, Pennsylvania, and Michigan—though they remain on the radar.
1. Nevada—Dean Heller (R) (Previous ranking: 1)
Heller is by far the most vulnerable Republican senator, but national headwinds, a Democratic-leaning state, and an opponent with a short voting record to pick apart also make him more endangered than any of his Democratic colleagues running in red states. That was reflected in a Reno Gazette-Journal poll released Tuesday that showed him at 41 percent and leading Rep. Jacky Rosen by just a point. His first TV ad, launched last week, focused on the ultimate bipartisan issue, veterans, which a supportive, McConnell-aligned outside group is simultaneously on the air discussing. Meanwhile, Rosen’s first negative ad, released in mid-July, hit Heller for flip-flopping on his support for repealing Obamacare. Rosen outraised Heller in the second quarter by more than $1 million, though the senator still led in cash on hand.
2. North Dakota—Heidi Heitkamp (D) (4)
Heitkamp, seeking her second term, has perhaps the most well-defined image of any senator up for reelection. Her early fundraising advantage has allowed her to go up early on the state’s cheap TV markets highlighting her independence. But the Democrat is down in early public polling, thanks to Republican Rep. Kevin Cramer’s statewide name ID and the partisan lean of a state that voted for Trump by 36 points. Cramer and the National Republican Senatorial Committee have both aired TV ads tying Heitkamp to national Democrats like Hillary Clinton and Schumer in hopes of continuing the state’s rightward trend.
3. Indiana—Joe Donnelly (D) (2)
Six years after defeating controversial GOP nominee Richard Mourdock, Donnelly faces a more viable nominee in Mike Braun. The distributing-company founder largely self-funded his primary bid, in which he upset two members of Congress, and entered the general election with a slight lead in a May poll. Donnelly released early ads displaying his bipartisanship in a state where Republicans swept statewide contests in 2016. Both sides already accuse the other candidate of outsourcing, presaging a nasty fall contest.
4. Missouri—Claire McCaskill (D) (3)
While McCaskill is the first known candidate target of Russian interference into the midterm elections, Republicans have focused on her husband’s wealth in an effort to paint her as looking out for her own financial interests over those of her constituents. That general line of attack continued Monday in an ad from the Club for Growth, which tied past domestic-abuse allegations against McCaskill’s husband to the senator’s voting record. The incumbent is swamping state Attorney General Josh Hawley in fundraising, but the Republican lean of the state ensures this will likely remain close until Election Day.
5. Arizona—Open (R—Jeff Flake retiring) (6)
Republicans face multiple obstacles in their most vulnerable open seat, with a fractious primary and Democratic Rep. Kyrsten Sinema buoyed by a lead in general-election messaging, fundraising, and polls. Rep. Martha McSally, Washington Republicans’ preferred standard-bearer, has a comfortable lead in polling over immigration hard-liners Joe Arpaio and Kelli Ward but has shifted to the right ahead of the Aug. 28 primary. The state still favors Republicans, who were able to deliver for Trump and Rep. Debbie Lesko in a special election this year, albeit by relatively narrow margins.
6. Florida—Bill Nelson (D) (5)
The Schumer-aligned Senate Majority PAC has spent some $6 million on TV over the past three months helping ensure Nelson doesn’t drown under the millions in spending by Republican Gov. Rick Scott and his outside allies. Scott’s hundreds of millions in personal finances ensure he won’t be outspent, and the $14 million he contributed out of pocket by the end of June illustrates how much he’s willing to spend. Despite eight years in the governor’s mansion, $18 million in spending during the second quarter, and Nelson not running a single TV ad yet, polls continue to show a lead of a few points bouncing between the two candidates. That’s unlikely to change in the next 90 days.
7. West Virginia—Joe Manchin (D) (7)
Public polling over the past three months has continued to show Manchin taking about 50 percent and leading by at least high single-digits. That is partly a name-recognition advantage over Attorney General Patrick Morrisey, but it’s also illustrative of the longtime elected official’s strength as an incumbent. Manchin isn’t Hillary Clinton, who lost the state by 42 points and to whom Republicans will do everything they can to tie the senator. The GOP caught a break when former Republican candidate Don Blankenship was ruled ineligible to run on a third-party line, but they’re still banking on Morrisey being stronger than what Manchin faced in 2010 and 2012, when linking him to President Obama proved fruitless.
8. Montana—Jon Tester (D) (9)
The Republican line of attack against Tester is that he isn’t the same guy voters sent to Washington 12 years ago. It hits straight at the senator's greatest asset—his profile as a farmer and average Montanan. While also criticizing Tester during their appearances in the state over the past few weeks, Trump and Vice President Mike Pence defended the Montana bona fides of GOP state Auditor Matt Rosendale, whom Democrats have labeled “Maryland Matt,” citing his move to the state in 2002. Benefiting from a 10-to-1 cash edge, Tester’s media campaign so far has talked up his leadership on veterans' issues and targeted Rosendale on health care.
9. Tennessee—Open (R—Bob Corker retiring) (not ranked)
Republicans’ only other competitive open seat provides a narrow pickup opportunity for Democrats on a map that lacks much room for the party to grow. Former Democratic Gov. Phil Bredesen raised as much as Republican Rep. Marsha Blackburn in the second quarter and leads some early polling after leaving office eight years ago. The former Nashville mayor went on TV early introducing himself as a business-friendly pragmatist with the help of millions in self-funding. Blackburn, who is seen as more conservative than the typical statewide elected official there, has also stockpiled more than $7 million, enough to get her message out in the final stretch.
10. Wisconsin—Tammy Baldwin (D) (8)
Wisconsin has a penchant for surprises, including Trump’s and Sen. Ron Johnson’s victories there in 2016. Since then, Democrats have won a series of down-ballot elections while Republican outside groups batter the state with millions of dollars in ads attacking Baldwin, a liberal first-termer. Republicans will pick between state Sen. Leah Vukmir and first-time candidate Kevin Nicholson, a former Democrat, in their Aug. 14 primary, giving the nominee less than three months to focus on the incumbent.