President Trump has been the most potent force in Republican primary elections, elevating allies and foiling foes with endorsements, social media posts and rally appearances.

But as the end of primary season draws near and the sprint to the general election begins, Mr. Trump may soon be something entirely different for Republican candidates. A liability.

The president’s approval rating is well underwater, dragged down by rising prices and an unpopular war. And Democrats have made clear that they hope to target Republican candidates in battleground races by tying them to Mr. Trump, believing they can ride voter anger with his administration to congressional majorities.

Yet Republicans in competitive contests may still need him. Even as they look for ways to distance themselves from Mr. Trump to appeal to swing voters, they must also weigh the president’s hold on their party’s base and his tendency to lash out at Republican dissenters.

“It’s a difficult one,” said Brendan Steinhauser, a Republican strategist in Texas, adding that the president’s approach to the primaries had probably made the dilemma harder for candidates, but predicting they would increasingly seek separation from him. “I think it’ll be very subtle. I think it’ll be district by district.”

Many Republicans are hoping for financial support from the president’s well-funded but tightfisted super PAC, MAGA Inc., which came to the rescue of Senator Darline Graham in her hotly contested Republican runoff this week. The group flooded the contest with more than $800,000 worth of voter calls and text messages.

There are signs of deeper involvement to come in races against Democrats. At a meeting in the Oval Office this month, Mr. Trump met with senior advisers and a small number of ad makers who had signed up with MAGA Inc., according to two people briefed on the meeting, who spoke on the condition of anonymity to describe a private conversation. The existence of the meeting was first reported by The Atlantic.

The gathering included a discussion about Democrats’ plans to make the election a referendum on Mr. Trump, and the president made clear that he wanted the advertising to include a robust defense of his record, according to the people briefed on the meeting. It was unclear how big of a share commercials focused on Mr. Trump would take of a fall ad campaign.

Spending by the group could be a welcome development for Republicans. As political headwinds have strengthened against them in the spring and summer, they have been holding out hope that MAGA Inc. would begin to invest in a challenging midterm cycle. But a rush of spending could also offer another way for the president to tighten his grip on the party — and on candidates who are angling for a measure of independence.

Mr. Trump, who has managed to revive his standing after past spells of widespread unpopularity, has started to put himself at the center of the midterms. He has urged supporters to “pretend” he is on the ballot and suggested he will spend significant campaign cash reserves.

Democrats are just as eager for him to play a starring role. Representative Jamie Raskin, Democrat of Maryland, argued that congressional Republicans had been boxed in by the president and rendered little more a rubber stamp for his agenda.

“Donald Trump controls the Republican caucus in Congress like a bunch of trained seals,” Mr. Raskin said Wednesday as he headed to a campaign event for Dr. Abdul El-Sayed, a candidate for Senate in Michigan. “This is essentially what the November elections are about.”

The President’s Untapped War Chest

One of the biggest variables on the minds of Republicans is money. The president has kept them guessing about how MAGA Inc. might deploy its massive war chest.

Mr. Trump continues to fund-raise, but he has been far less willing to part with the record sums he has accumulated.

“I’ll be spending a lot of that money and my own money,” Mr. Trump told reporters last week, though he has not spent any of his personal funds on politics in a decade. “But I’ll be spending a lot of that money for candidates that I think are good.”

At a briefing for Republican senators in early August by two of Mr. Trump’s advisers and the leader of the Senate Republican super PAC, the Trump team left the strong impression that money was coming imminently as they offered messaging advice, according to two people who attended the meeting and spoke on the condition of anonymity to describe a private discussion.

But in the weeks since, MAGA Inc. has not been spending in Senate battlegrounds states, and some Republicans are growing anxious that races in North Carolina and Georgia may be falling out of reach.

“MAGA Inc. is sitting on a small nation’s G.D.P., and certainly their money is welcomed,” said Mike Hahn, a Republican strategist working for the party’s Senate nominee in Georgia, Representative Mike Collins. He said he would welcome Trump-focused ads in Mr. Collins’s race against Senator Jon Ossoff.

‘Pretend, Please, That I’m on the Ballot’

A number of battleground Republicans — including former Representative Mike Rogers of Michigan, a Senate candidate; Representative Mike Lawler of New York; and Representative Derrick Van Orden of Wisconsin — have joined the president at events since the spring. Others have said they would be open to it.

A spokesman for the National Republican Congressional Committee, Mike Marinella, said House Republicans were eager to campaign with the president because of his ability to energize the party’s base.

Still, some Republicans have shown little visible interest. They include Senator Susan Collins of Maine and the Senate candidate Michele Tafoya of Minnesota. And in Iowa, Representative Ashley Hinson, a Trump ally running in a competitive Senate race, has pushed back on his decision to allow beef to be imported into the United States with lower tariffs.

The White House has said that the president is committed to maintaining Republican majorities and that its policies have given the party a compelling platform to run on. “There is a great story to tell,” Olivia Wales, a White House spokeswoman, said in a statement, pointing to steep decreases in crime and the Trump administration’s immigration crackdown.

It is not yet clear how much pressure Mr. Trump might place on vulnerable Republicans to offer him total loyalty. Nor is it clear how interventions by Mr. Trump in favor of members of his party in competitive general-election races would play with voters.

Republicans have found reasons for disappointment in each of the last the two cycles when Mr. Trump himself was not on the ballot, losing the House in the 2018 midterm elections and failing to recover the Senate in the 2022. (They did win the House in 2022.)

Mr. Trump has pointed to those outcomes as he pushes voters to turn out in the midterms.

“They say that ‘Trump does great when he’s on the ballot, but when he’s not on the ballot, his people don’t come,’” the president said at a rally in South Carolina last week. He added, “So what I really want you to do is pretend, please, that I’m on the ballot. Just come and vote.”

Days later, Mr. Trump showed he could draw enough Republicans to the polls to elevate Ms. Graham in the Senate primary runoff, even after she fumbled in a debate when she admitted to not being “that informed on national security.”

A Primary Season With November Implications

Mr. Trump’s actions during primary races could influence the November election.

The president spent the spring on a retribution tour, investing heavily in his successful efforts to oust Senators Bill Cassidy of Louisiana and John Cornyn of Texas, as well as Representative Thomas Massie of Kentucky. Mr. Cassidy and Mr. Massie hail from deeply conservative areas, while Mr. Cornyn’s state is seen as increasingly competitive.

Mr. Trump’s effort to oust Mr. Cornyn, who had said in 2023 that Mr. Trump’s time had “passed him by,” helped hand the Republican Senate nomination to Ken Paxton, the scandal-plagued Texas attorney general. Many Republicans say that Mr. Paxton could offer Democrats an opportunity to win a Senate seat in Texas for the first time in decades.

The president has been more restrained in targeting other battleground Republicans. In March, he restored his primary endorsement of a Colorado Republican, Representative Jeff Hurd, after his short-lived support for a right-wing challenger generated backlash from Republicans who warned it would imperil the seat in November.

The episode underscored Mr. Trump’s competing impulses — a desire for party fealty and a fear of losing Congress in the midterms. Mr. Hurd had criticized the president’s tariff policies, plainly irritating him. But Mr. Trump still backed down.

And even if candidates like Ms. Collins, who is running for re-election in Democratic-leaning Maine, may be granted more space for dissent by the president, they may also find it hard to disentangle themselves from his falling standing.

“Like it or not, politics today is about President Trump,” said Allen Fuller, a Republican consultant in Colorado, adding: “In the past you could localize your campaign and run a good ground game, do a lot of in-district events and you’d be OK. You can’t do that in 2026.”

Democrats say that general-election voters across the country will punish Republicans who have tied themselves to the unpopular president.

“Republicans have been unwilling to stand up to Trump policies,” Senator Kirsten Gillibrand, the chair of the Senate Democrats’ campaign arm, said in an interview last week. “Voters are going to vote differently. If they voted for Trump the last time, I don’t know that they’ll vote for a Republican this time.”

Zolan Kanno-Youngs contributed reporting.