Senate rankings: Here are the 5 seats most likely to flip

Midterms were only six months ago, but the 2024 campaign season is already firing on all cylinders as races ramp up for the Senate seats that will determine control of the upper chamber.

Republicans are on offense as they search for the top candidates to take down a cadre of incumbent Democrats who have survived cycle upon cycle. At stake is the Democrats’ one-seat majority as they play defense in ruby-red states that Republicans are licking their chops to win. 

Here’s an early look at the five Senate seats most likely to flip next year:

West Virginia

West Virginia Gov. Jim Justice speaks during an announcement for his U.S. Senate campaign on April 27 at The Greenbrier Resort in White Sulphur Springs, W.Va. (AP Photo/Chris Jackson)

The state has long been expected to be at the center of the fight for the Senate, but that battle heated up last week when Gov. Jim Justice (R) announced his bid to replace Sen. Joe Manchin (D-W.Va.), handing the GOP one of its top recruits on the 2024 map.

Justice immediately becomes the favorite for the GOP nod. Polling is showing him likely to prevail, and the National Senatorial Campaign Committee and Senate Leadership Fund (SLF), backed by allies of Senate Minority Leader Mitch McConnell (R-Ky.), are signaling their support.

Top senators are also on board, including Sen. Shelley Moore Capito (R-W.Va.), who appeared with Justice on Thursday night and labeled him a “powerhouse.” 

But he still faces a tough road against Rep. Alex Mooney (R-W.Va.), a pro-Trump conservative who showed his mettle last year by ousting then-Rep. David McKinley (R-W.Va.) in a primary spawned by redistricting. The Club for Growth has also said they are prepared to drop $10 million to back Mooney. 

“Justice is 50-50 to just be the nominee,” one Democratic operative told The Hill, noting that the governor was a Democrat not long ago. 

The winner of the primary takes on Manchin in a state former President Trump won by almost 40 points.

Manchin has been both a linchpin and thorn in the side of Democrats, delivering key votes last year for major pieces of legislation but first extracting concessions from leadership. More recently, he said he is prepared to support overturning the Inflation Reduction Act if the administration does not implement it properly and voted with Republicans to overturn a Biden administration rule on truck emissions. 

The two-term moderate Democrat says he won’t decide on a run before December and is likely to watch the primary and see how things unfold before making the call. 

But Republicans are gearing up as if Manchin will be on the ballot once again.

“Sen. Manchin is formidable. We all know that,” Capito said in a brief interview. “It’ll be a barnburner, that’s for sure.”

Manchin, for his part, issued a statement shortly before Justice announced his run, both boasting of his electoral prowess and contributing to speculation he may have other aspirations.

“But make no mistake, I will win any race I enter,” he said.

Montana

Rep. Ryan Zinke (R-Mont.) leaves a closed-door House Republican Conference meeting on Feb. 28 at the Capitol Hill Club in Washington, D.C. (Greg Nash)

Unlike in West Virginia, the first half of the equation is complete for Democrats as Sen. Jon Tester (D-Mont.) announced earlier this year that he will seek a fourth term, giving the party a real chance in one of the two reddest states on the map. 

Now, it’s a matter of getting him across the finish line as Republicans try to find a candidate able to deny him six more years in Washington. 

For the GOP and National Republican Senatorial Committee (NRSC) Chairman Steve Daines (R-Mont.), the two names that continue to pop up are businessman Tim Sheehy, a friend of Daines and Rep. Ryan Zinke (R-Mont.), and Montana Attorney General Austin Knudsen (R) as they try to find someone (and anyone) who isn’t Rep. Matt Rosendale (R-Mont.) to square off with Tester.  

“We need to get the right candidate in a state like that. … Rosendale can’t do it,” one GOP operative said, adding they suspect Tester ran in part because of the chances Rosendale would win the nomination.

Tester defeated Rosendale by 4.5 points in 2018. 

Despite the state’s red hue — Trump won the state by 16 points in 2020 — Democrats remain confident in Tester, who is trying to keep his focus on all things local. Last week was a prime example as he announced a blockade of all Biden administration nominees to Amtrak’s board of directors over the lack of Western representation.  

“No matter who his opponent is, they’re not from Montana,” the Democratic operative said. “There’s nobody more Montana than Jon Tester.” 

Ohio

Sen. Sherrod Brown (D-Ohio) arrives for an all-Senators briefing on April 19 at the Capitol in Washington, D.C., to discuss the documents leaked on a Discord chatroom by Massachusetts Air National Guardsman Jack Teixeira. (Greg Nash)

The Buckeye State fills out the political triumvirate of incumbent Democrats in red states that the GOP is trying to knock off as Sen. Sherrod Brown (D-Ohio) tries to nab a fourth term. 

So far, two top-tier candidates have jumped into the race to replace Brown — Matt Dolan and Bernie Moreno, both of whom ran in 2022 — while two others — Ohio Secretary of State Frank LaRose and Rep. Warren Davidson — are eyeing potential bids. 

Most are considered viable candidates to defeat Brown, though questions remain about Davidson given his lack of financial prowess or statewide name-ID. 

“It’s wide open. Even more wide open than last time,” a second GOP operative told The Hill. “If you don’t have $10+ million, it’s almost not plausible [to complete]. That’s the first, second and third hurdle for anyone.”

Republicans believe Brown will be tough to take out, no matter who emerges. But they are leaning on the shift to the right the state has undergone over the last eight years to carry the day for them.

“Very tough,” the second operative said of how difficult it will be to topple Brown. “He has never run in the new Ohio — in the ruby red Ohio. … The wind has always been at his back, it’s never been at his face, but he’s not to be underestimated.” 

Arizona

Sen. Kyrsten Sinema (I-Ariz.) arrives for an all-Senators briefing on April 19 at the Capitol in Washington, D.C., to discuss the documents leaked on a Discord chatroom by Massachusetts Air National Guardsman Jack Teixeira. (Greg Nash)

The Arizona Senate race is by far the most complicated contest on this list as questions surround the future of Sen. Kyrsten Sinema (I-Ariz.), who left the Democratic Party last year and has not said whether she’ll mount a reelection bid.

Sinema this week once again demurred when asked during an interview about her future plans. 

But as things stand, a three-way race is shaping up between her, Rep. Ruben Gallego (D-Ariz.) and an unknown Republican, with murmurs centering on whether former GOP gubernatorial nominee Kari Lake will seek the seat. 

If she does, she is the likely favorite to win the party nomination over Pinal County Sheriff Mark Lamb, who officially launched his bid earlier this month. 

But if she doesn’t, the door opens to a possible reprisal bid by Blake Masters, who lost to Sen. Mark Kelly (D-Ariz.) in 2022, and Jim Lamon, who was defeated by Masters in the primary. 

Establishment forces, meanwhile, are holding out hope that Karrin Taylor Robson, who lost the GOP gubernatorial primary to Lake last summer, will run. One Arizona-based GOP operative said that she is “really considering” that possibility. 

“It’s a really big mess,” the first GOP operative said. “That field is far from set. … Among the races that should be getable, it’s going to be the toughest.” 

While Gallego is considered the favorite in the race writ large given the uncertainty surrounding Sinema and Lake’s likely struggles to win moderate support, some figures don’t count the incumbent senator out when all is said and done. 

“The secret sauce is that she’s like teflon. Nothing sticks to her. … But is she a spoiler or can she win? It’s too early to know,” the Arizona-based GOP operative said. ”She is tenacious. She is smart and she will work hard. The question I’ve been asking is: How much does she want it?”

National Democrats are still refusing to put their finger on the scale yet and the Democratic Senatorial Campaign Committee is telling donors to lay low as they await Sinema’s decision, the Democratic operative said. 

Pennsylvania

Sen. Bob Casey (D-Pa.) is seen during a Senate Health, Education, Labor and Pensions Committee hearing on March 22 to discuss the upcoming price hike for Moderna’s COVID-19 vaccine. (Greg Nash)

Of the five Democrats on this list, no one is in a better position to secure reelection than Sen. Bob Casey (D-Pa.) as Republicans brace for a bruising primary battle between the establishment and hardcore right-wing factions of the party.

Ask almost any Republican in the Keystone State and they’ll say the GOP’s chances to defeat Casey are zilch if David McCormick, the former CEO of Bridgewater Associates who lost the state’s Senate primary to Mehmet Oz last year, isn’t the nominee.

McCormick has said for months that he is undecided about a bid, but he’s done everything in that time to tee himself up for another run, including meeting with party leaders across the state and releasing a book. 

He also has the full backing of the NRSC and SLF to boot. 

“He’s worked very hard at being visible, being at the right places talking to the right people and is prepared to run a race he wasn’t last time around,” one Pennsylvania-based GOP operative said. “[The 2022 primary] wasn’t a race he built a base for. This time he has a base.”

However, the possibility of a primary bid by state Sen. Doug Mastriano (R), who Gov. Josh Shapiro (D) defeated by nearly 15 points in November for the right to lead the state, continues to be of concern for many within the party who worry he would cost the party the seat outright if he is the nominee. 

Even former President Trump is reportedly worried about the possibility as Mastriano continues to float a possible bid.