The Senate battlefield is set after Tuesday’s primaries, with both parties bracing for a close — and expensive — fight for control centered on a handful of key states.

After GOP Sen. Rick Scott and Democratic former Rep. Debbie Mucarsel-Powell advanced to the general election in red-leaning Florida, the key November races on the Senate map are officially set, most of them in Democratic-held territory. 

Democrats are optimistic they can hold their narrow majority, buoyed by the fresh wave of enthusiasm Vice President Kamala Harris’ candidacy has provided and the strength of the brands incumbent senators have built in their home states. But Republicans still see a broader playing field tilted in their favor, betting voters’ partisan loyalties will overwhelm Democrats in must-win states that have trended toward the GOP. 

Republicans need a net gain of just two seats for an outright majority or one if former President Donald Trump wins the White House, because the vice president casts tiebreaking votes in the Senate. 

The GOP can effectively already count one in its column thanks to Democratic Sen. Joe Manchin’s decision not to run for re-election in heavily conservative West Virginia. And the GOP has two prime targets in states Trump easily carried four years ago: Sens. Jon Tester of Montana and Sherrod Brown of Ohio.

“Senate Democrats need to pitch a perfect game to hold their majority, including in ruby red Montana and Ohio,” National Republican Senatorial Committee Chairman Steve Daines, R-Mont., said in a statement. “We like our odds.” 

Democratic strategist Martha McKenna, a veteran of the Democratic Senatorial Campaign Committee, countered, “The map might be hard, but our starting pitchers, to extend the metaphor, are the best we’ve got in the business.”

“We’ve had five or six perfect innings,” McKenna added later. “And now we’ve just got to close.”

Partisanship vs. incumbency

Sen. Gary Peters, D-Mich., chair of the Democratic Senatorial Campaign Committee, said in a recent interview that he believes his party can hold 50 seats, acknowledging West Virginia is no longer in play. But he added that he is “very optimistic” Democrats can pick up one or two seats controlled by Republicans in Florida and Texas.

To do that, Tester and Brown will most likely have to do what few have accomplished in the hyperpolarized Trump era: win their states as their voters support a candidate from the opposite party for president. Only Sen. Susan Collins, R-Maine, pulled that off in 2020. And no Senate candidates did it in 2016. 

But Democrats believe that if anyone can persuade voters to split their tickets, those two senators can.

“They have always had to run above the Democratic base,” Peters said. “They’ve done it in the past. I’m confident they’re going to do it again in the future.” 

While partisan polarization has been a strong force, so has the power of incumbency. No senators lost their re-elections in the 2022 midterms. Five lost in 2020, and just two lost in 2016. 

But Democrats have a tough road ahead defending not just those two red states but also several perennial battlegrounds, including Pennsylvania, Nevada, Arizona, Wisconsin and Michigan. And they plan to make the fight personal. 

“We have superior Democratic incumbents and candidates running against flawed Republican candidates,” Peters said, adding later that voters “have a choice between two individuals, and they’ll weigh the pluses and minuses on those individuals. And when they do that, we’re confident they’re going to vote for the Democratic Senate candidate.” 

The Democratic Senatorial Campaign Committee has launched a flurry of ads this month taking aim at GOP candidates’ personal backgrounds, delving into their business dealings and raising questions about their ties to the states they are running in. 

But Republicans believe they have strong recruits, pointing to candidates with military backgrounds like Montana’s Tim Sheehy and Pennsylvania’s Dave McCormick. Those two Republicans, along with other contenders, are also personally wealthy and can fund their own campaigns as they face a tidal wave of Democratic money. 

National vs. local emphasis

As Democrats have tried to localize and personalize the campaign, the GOP has sought to nationalize it.

The National Republican Senatorial Committee has teamed up with GOP candidates on a slew of ads tying Democrats to Harris and President Joe Biden. (The spots are known as hybrid ads, which must partly focus on national issues.)

Harris’ new status as the presidential nominee has given Democratic Senate candidates a much-needed energy boost, bringing in new volunteers and campaign donations.

Public polling had found Democratic Senate candidates performing better than Biden before he decided to drop out of the race. And while some are still outrunning Harris, their paths are clearer without such a wide gap at the top of the ticket. 

“I think we had excellent matchups even before the switcheroo, but now it’s like everybody chugged a Red Bull,” said McKenna, the Democratic strategist. 

Peters also said Harris’ ascension has led to “tremendous energy across the Democratic base and including independents, who are very excited about having a young, dynamic candidate running for president. And so that will certainly help everyone.” 

That enthusiasm could boost Democrats as they look to expand the Senate battlefield to Texas, where GOP Sen. Ted Cruz faces Democratic Rep. Colin Allred, and Florida, where Scott is seeking a second term against Mucarsel-Powell. 

Democrats have so far not devoted any significant resources to either state, according to the ad tracking firm AdImpact. But Peters is not ruling it out. 

“Clearly, my first priority is to hold all of our Democratic incumbent seats, and that’s where our majority of our investments are being made right now,” Peters said. “But we also want to go on the offense, and we’ll make investments as we see opportunities arise.” 

Republicans, meanwhile, say the fight for the Senate has not dramatically shifted even with the change at the top of the ballot.  

“Although there’s been a lot of changes in the last six to eight weeks in the national environment, I do think that this Senate picture is remarkably stable,” said GOP strategist Josh Holmes, a former chief of staff to Senate Minority Leader Mitch McConnell, R-Ky.

Holmes noted that Republicans have stayed focused on their key pickup opportunities, not repeating the mistakes from 2022 of trying to expand the Senate map. 

“From our standpoint, we knew that it’s just going to be a dogfight the whole way,” Holmes said, adding that campaigns, party committees and outside groups have “prepared as though this is a fight for one seat, two seats, three seats, not a fight to get to 55 or 60.”

Republicans are still cautiously optimistic about their chances in Maryland, with GOP former Gov. Larry Hogan’s history of winning the deep-blue state. But while they had been looking at some possible targets in Democratic-leaning states like New Mexico, that path is less feasible without Biden dragging down his fellow Democrats. 

“You have to have an environment that’s with the wind to your back,” said a GOP strategist who has worked in Senate races, who was granted anonymity to discuss party strategy. “And I just don’t think that’s where we are right now.”

With Harris at the top of the ticket, down-ballot Democrats have been more willing to campaign with their presidential nominee.

Democratic Sens. Tammy Baldwin of Wisconsin, Bob Casey of Pennsylvania and Jacky Rosen of Nevada, as well as Reps. Elissa Slotkin of Michigan and Ruben Gallego of Arizona, both running in open-seat contests, all appeared at Harris’ rallies in the opening days of her campaign. 

GOP Senate candidates have long tied themselves to Trump. All of the top candidates, except Hogan, spoke at the Republican convention last month, a sign of how closely their fights are tied to Trump. 

“You’re dealing with a bunch of really tight races where ultimately the choice between voters is going to be whether you like the way things are going or you want to go back to a 2016, 2017, 2018, 2019-style economy,” Holmes said. 

Republicans believe voters’ concerns about the cost of living, immigration and crime will work in their favor up and down the ballot. And Democrats see abortion as a top issue across the map, possibly boosting Senate candidates in states that have measures on the ballot to codify abortion rights protections, like Florida, Arizona and Nevada. 

But Democrats still acknowledge that there is a tough fight ahead. 

“It’s a challenging map,” said a Democratic strategist involved in Senate races. “It will be a challenging map right through Election Day.”