The 2024 battle for the Senate started with a bang earlier this year and has not let up, as candidates in top races continue to roll out their campaigns and incumbents scratch and claw to win reelection. Their efforts will determine who will control the upper chamber for the next two years.

Democrats are trying to play defense in a number of red-leaning states to hold on to their one-seat majority, while Republicans fight recruiting battles in several states to give them the best shot at winning a majority.

While it is too early to tell which side’s maneuvering will pay off, here’s a midsummer rundown of the five Senate seats most likely to flip next year.

West Virginia 

The top spot in these rankings remains unchanged as Sen. Joe Manchin (D-W.Va.) faces a true uphill battle to retain his seat and secure a third full term in the Senate.

Republicans have been licking their chops at the possibility of unseating Manchin and, unlike in 2018, they seem to have their best candidate in place to do just that in West Virginia Gov. Jim Justice (R). An East Carolina University (ECU) survey released in late May shows Justice leading the incumbent centrist Democrat by more than 20 percentage points. 

In order for Justice to make it that far, he must overcome a potentially tricky challenge against Rep. Alex Mooney (R-W.Va.), who is backed by conservative forces. The ECU poll also shows Justice with a 40-point lead over Mooney, though some of that advantage is owed to his massive name ID. 

Facing political challenges back home, Manchin has been on an offensive against President Biden’s spate of nominations in recent months, having said that he will oppose all his Environmental Protection Agency (EPA) nominees and voted against multiple judicial selections in recent weeks. He also opposed Biden’s choice of top economic adviser and is likely to oppose Julie Su’s nomination to lead the Department of Labor, if she ever comes up for a vote on the floor.

Allies, however, say this isn’t anything unusual and that it’s just how he operates.

“The recent opposition is just who he normally is. He reviews all nominees the same way,” said Jon Kott, a former Manchin spokesperson, who noted what Manchin used to tell him about how he considers nominees. “He’d say, ‘I look at them and say: Are they good for the state of West Virginia and the good of the country?’”

“I just think it’s getting more scrutiny because it’s the political season,” Kott added. 

Of course, Manchin has yet to announce whether he’ll even seek reelection, with a decision expected in December or shortly before the January filing deadline, as he continues to flirt with a third-party presidential bid. 

Montana

It was a big week in Big Sky as Tim Sheehy, a retired Navy SEAL turned businessman, threw his hat into the ring and gave Republicans their best hope to finally defeat Sen. Jon Tester (D-Mont.) next year.

Sheehy is among the top recruits this cycle for Sen. Steve Daines (R-Mont.), the chairman of the National Republican Senatorial Committee, who badly wants to topple the three-term Montana Democrat. The newly minted GOP candidate has a lot of things going for him, headlined by his business background, military service and bank account largesse — a trio that Republicans argue is sterling.

Strategists argue that while he looks great on paper, first-time, millionaire candidates can have trouble resonating with voters. This was seen last cycle when David McCormick in Pennsylvania was unable to escape the primary and has since lamented that he didn’t find his sea legs until it was too late. Ironically, he, too, is atop Daines’ wish list this year.

But for now, Republicans are flying high over Sheehy.

“It’s been proven that Tester is tough and if we’re serious about winning the seat, we need to put forward our best candidate,” one national GOP strategist told The Hill. “It’s pretty clear he doesn’t want to run against Sheehy, and that should tell you all you need to know.”

Sheehy will likely have to prevail over Rep. Matt Rosendale (R-Mont.) in a primary, with Democrats itching for a Tester-Rosendale rematch after the incumbent senator defeated him by 3.5 percentage points. Rosendale has a pocket of right-wing support and name ID after multiple statewide runs, but he has numerous issues — including lackluster fundraising and a Maryland accent that caused him issues during his last Senate bid, to name a few. 

Ohio

Rounding out the trio of the seats Republicans are most hopeful to flip is the Buckeye State, where they likely have their best chance to beat Sen. Sherrod Brown (D-Ohio).

Brown has proven to be a difficult out for Republicans in each of his reelection fights, which he won by 6 and 6 percentage points, respectively. However, Ohio has moved further to the right in that time, with former President Trump carrying the state by 8 percentage points in 2020, despite losing the election. Put simply, the swingiest of swing states has gotten redder than ever, but whether that will be enough to take down Brown remains to be seen.

For now, only two top-tier Republicans — state Sen. Matt Dolan and Bernie Moreno — have announced bids, with another likely to come from Ohio Secretary of State Frank LaRose (R). LaRose is expected to jump in the race in July, one Ohio GOP source told The Hill, creating a tough three-way contest that will have a number of balls in the air. 

Asked to forecast a three-way primary, the Ohio GOP source said that Moreno will likely win Trump’s endorsement and that LaRose could have fundraising issues, especially given that he’s the only one of the group who can’t self-fund, as he’s noted.

“Moreno is the favorite, but as a first-time candidate, he will likely make some mistakes,” the source said. “The question is: is that enough of an opening for either of the two others?”

Arizona 

Of the states on this list, perhaps no race has changed less than the battle in Arizona, as Rep. Ruben Gallego (D-Ariz.) remains the top choice of Democrats, Kari Lake is the likely option for Republicans even though she has yet to announce a bid, and Sen. Kyrsten Sinema (I-Ariz.) has yet to tip her hand and say whether she will seek reelection next year as an independent.

Gallego announced his bid in late January and has put himself in as good of a spot as a Democrat can at this point in time. The Arizona Democrat posted a strong $3.7 million haul in the first quarter, outraising Sinema by $1.6 million during that stretch and giving Democrats hope that they can retain the seat next year. He also received a boost on the left last week, as former Speaker Nancy Pelosi (D-Calif.) endorsed his bid. 

“He seems to be doing what he needs to be doing. Head down. Building his brand,” one Democratic operative with Arizona ties told The Hill, noting that Gallego has so far avoided a bruising primary with Rep. Greg Stanton (D-Ariz.) declining to run. 

On the GOP side, all signs still point to Lake, who has effectively frozen the field until she decides whether to take the Senate plunge as she falsely argues that she is the “lawful governor of Arizona” after her loss to Gov. Katie Hobbs (D) in November.  

However, Lake has taken steps toward a possible bid, having met with more than a handful of GOP senators during a mid-May visit to Washington. Pinal County Sheriff Mark Lamb has also entered the GOP primary. 

Meanwhile, the wait is on for Sinema, who filed paperwork for a bid but has stayed mum when asked in various interviews about her 2024 plans. Her impact on the race remains a massive unknown as a three-way general election battle opens up doors not previously seen in races in the state. 

“It’s hard to say one way or another,” the Democratic operative said about a three-way race.

Wisconsin

Finally, Wisconsin is the lone new entrant on the list as Sen. Tammy Baldwin (D-Wis.) tries to secure a third term and Republicans try to figure out who will be their best candidate to deny her six more years in office.

Just like the other Democratic incumbents mentioned above, Baldwin has proven to be a real challenge for Republicans in each of her Senate bids. After defeating former Wisconsin Gov. Tommy Thompson (R) to win her seat in 2012, she followed that up with an impressive double-digit win in 2018, giving Democrats another battle-tested member to lean on in what could be a tough cycle.

“What makes Baldwin incredibly hard to beat is that she puts in the work and she’s got 15 winning campaigns to show for it,” said Joshua Karp, a Democratic operative who advised Wisconsin Lt. Gov. Mandela Barnes’ (D) campaign last year. “Wisconsin’s a state where people expect to have a personal relationship with their leaders and Baldwin puts in the personal touch and it shows.”

Republicans have been wading through possible options. However, they were dealt a blow in recent weeks as Rep. Mike Gallagher (R-Wis.) announced he would seek reelection in the House and focus on his work atop the newly created Select Committee on China. 

Now, they are looking at a pair of self-funders to take Baldwin on. 

Eric Hovde, a former hedge fund manager who narrowly lost the 2012 Senate primary to Thompson, is considered the leading figure, as he would be buoyed by a massive war chest and experience running a statewide campaign. One Wisconsin GOP operative noted recently that Hovde has floated spending at least $20 million of his own money. 

The second self-funder looking at a run is businessman Scott Mayer, who will likely make a decision post-Labor Day. The downside: He has nearly zero name ID in the state. Sen. Ron Johnson (R-Wis.) recently acknowledged that he doesn’t know Mayer very well, either. 

Rep. Tom Tiffany (R-Wis.) is also considered an option, though he’d have to give up his ruby-red seat to jump in the race.

What will be the key to Republicans ousting Baldwin, though, will be external forces. What will Biden’s standing be in the state next year? And will the GOP nominate Trump, Florida Gov. Ron DeSantis (R) or someone else next year? Those are questions that will weigh heavily on the Senate race. 

According to a new Marquette University Law Poll, DeSantis is deadlocked with Trump and would fare better in a one-on-one matchup against the president. That would give Republicans a better shot at holding the seat.