With the midterm elections just over three weeks away, the fight for control of the U.S. Senate is intensifying in battleground states, as Democrats push into red regions and Republicans pour money into key contests. Campaigns are entering a crucial stretch for persuading the independent voters who will probably determine outcomes in swing races. Nearly all of the most competitive Senate races are in states with significant swaths of people unaffiliated with either major party — the “kingmakers” in these high-stakes midterms, said Jeremy Gruber, an independent-voting expert.

"Independent voters are going to be deciding this election in every respect," said Gruber, senior vice president of Open Primaries, an organization that advocates for states to open primary elections to unaffiliated voters. The urgency around courting nonaligned voters has been on display at recent debates, in ads flooding the airwaves and in the campaign money pouring into key states. For Republicans, it has become an effort to put distance between themselves and President Trump; for Democrats, it's often a rhetorical shift toward the center and away from the far left.

In Iowa, Republican Ashley Hinson used a Wednesday night debate to emphasize her willingness to break with Trump. In Kansas, Democrat Adam Hamilton is circulating a video in which he describes himself as both liberal and conservative. In Alaska, a GOP-backed ad blitz launched last week aims to persuade voters that Democrat Mary Peltola isn’t independent-minded. Though many unaffiliated voters have made up their minds, those who remain undecided will begin making decisions soon, as mail ballots go out and early voting begins in some states.

"For Republicans who are running behind and are looking at a potentially devastating midterm election performance, what they really need to do is target the independents who lean Republican," said Karen Kedrowski, an Iowa State University political scientist.

"For Democrats in some place like Iowa ... what they need to do is make it seem safe [to independents] to vote for a Democratic candidate." Unaffiliated constituents have long been key to victory in swing states, particularly where races are traditionally decided by small margins. They have been viewed as particularly persuadable this year, as public dissatisfaction with Trump's economic policies puts the votes of swing voters who backed him in 2024 up for grabs.

Forecasters predict that Democrats are on track for the House majority and could hold a majority of gubernatorial seats for the first time since 2010. Though Senate control remains a toss-up, Democrats' chances are viewed by forecasters to have significantly improved since the summer. A set of New York Times/Siena polls reported last week showed Democratic candidates for the Senate ahead in Texas, Michigan, Alaska and Ohio and neck-and-neck in Kansas and Iowa — all states Trump carried in 2024.

Republicans, meanwhile, are feeling increasingly bullish about their chances in Maine, New Hampshire and Minnesota, all states that went blue in the last presidential election. Republicans hold a significant fundraising advantage, however, and party donors are pouring money into key races, hoping the spending can cut into the Democrats' edge. By September's end, GOP advertisers had more than doubled their spending compared with August, outstripping Democrats, according to tracker AdImpact.

Among the nine Senate races considered the tightest by forecasters, Republicans have outspent Democrats in all, AdImpact reported. But on Friday, the Cook Political Report, a leading election forecaster, moved 18 House races in Democrats' direction, saying that heavy ad spending by Republicans has not begun to move the needle in their favor. Democrats view themselves as in their "strongest position yet" to win the majority, Sen. Kirsten Gillibrand (D-N.Y.), who chairs the Democratic Senatorial Campaign Committee, said in a statement last week.

“In this final stretch of the election, Democrats will continue to vigorously campaign and fight for every vote across the expanded map," Gillibrand said. Republicans are confident about their ability to persuade voters in key states, said Bernadette Breslin, a spokesperson for the National Republican Senatorial Committee.

"Republicans will defend the Senate majority across key battlegrounds that have trended reliably red," Breslin said, "with candidates like Mike Rogers [in Michigan] and Roger Marshall [in Kansas] winning over independents by exposing their Democratic opponents' radical, unaffordable agendas." Along with the decisions of independent and swing voters, the midterm outcomes could also hinge on the level of turnout within each party, analysts say.

If a portion of the party faithful stay home in a given place — for instance, disillusioned conservatives in Kansas or frustrated Black Democrats in Michigan — that could swing individual races, analysts said. The number of independent voters reached a record high this year, with 45% of American adults identifying as political independents in Gallup polling. Equal shares identified as Republicans and Democrats, 27% for each party. The trend is partly driven by majorities of millennial and Gen Z voters choosing to be unaffiliated with either party, according to Gallup research.

Such voters make up a majority in Alaska and between 30% and 40% of alled voters in Maine, Iowa, New Hampshire, North Carolina and Ohio. They account for about 29% in Kansas and about 16% in Texas and Michigan, according to state data compiled by the Independent Voter Project. Across recent polls, independent voters have favored Democrats and expressed dissatisfaction with Trump.

In a late September poll from Emerson College Polling, 66% of independents said Trump has done worse than expected during his second term in office. In Texas, Democrat James Talarico led Republican Ken Paxton among independents by 32 points in a September poll by Texas Public Opinion Research. The Democratic candidate in Ohio, Sherrod Brown, led Republican Sen. Jon Husted by 27 points among independents in a CNN poll released Thursday.

In Kansas, where the Senate race has become unexpectedly close amid economic-driven anger with Trump, disapproval of the president's performance among independents appears to be rubbing off on incumbent Sen. Roger Marshall, the Republican seeking reelection. Fifty-two percent felt unfavorably toward Marshall and 62% disapproved of Trump's performance, according to a recent Emerson College/Nexstar poll. In those battleground red states, that creates a tough fight for both parties, analysts said.

With control of the Senate hanging in the balance, candidates are duking it out in fundraising and on the campaign trail to win every last vote. "Both campaigns are raking in ridiculous amounts of money ... and they're spending every penny because [they] have to," said Wichita State University political science professor Alexandra Middlewood, referring to the Kansas Senate race. "We see that they're really going to have to fight it out all the way to the end."

Debates are another tool for candidates to reach independent voters, said Corwin Smidt, a political science professor at Michigan State University. In Michigan, where the Senate candidates sparred in their first debate Thursday evening, Rep. Mike Rogers, the Republican Senate nominee, has distanced himself from Trump twice in recent weeks, first calling for an end to the war in Iran and then releasing an ad last week denouncing the tariffs against Canada. Democrat Abdul El-Sayed, meanwhile, announced a rally with former President Obama, an appeal to mainstream voters.

"They've got to try to both win over people who have been paying attention, but also introduce themselves to the ones who haven't been paying attention," Smidt said. Winning unaffiliated voters can require a tightrope walk for candidates who are faced with the dual tasks of appealing to their party base while persuading independent constituents. In the final stretch of the campaign, candidates seeking independent votes should telegraph a willingness to admit their party's flaws and an understanding that voters are turned off by partisan rhetoric, said Chad Peace, legal strategist at the Independent Voter Project, which advocates for open primaries.

"They have to communicate to those folks and try to meet them where they're at," Peace said. "[Independents] want the campaigns of persuasion, they don't want to hear you tell me how bad the other candidate is." And, Gruber said, they want to be engaged with, not ignored. "Independent voters," he said, "are going to be responding to those candidates and parties that actually talk to them."