His grip on Republican senators has held in the lead-up to a historic impeachment trial. Members of the House have faced the prospect of retiring before going against him. And he frequently boasts about his strong approval ratings among Republican voters.
Yet for a party leader who inspires fear in Washington, President Trump has been bedeviled by governor’s races time and again, even after his aggressive campaigning has helped Republican candidates win.
Unable to modulate his excitement for other people’s political battles — and, according to advisers, not understanding the distinct incentives for governors who run their own states and senators who have to work with him in Washington — Mr. Trump has plunged headfirst into contests that have done little but expose his own political vulnerabilities.
In the last month, two Republican candidates the president supported lost their off-year races for governor, puncturing his self-proclaimed role as kingmaker. But even his successes in the 2018 governor’s races have left him disappointed: The winners he championed, once in office, have defied his wishes and cast aside his allies, as recently as this past week.
“Fundamentally, unlike members of the House and the Senate, there’s no element of dependency that goes with being in Washington” for governors, said Mark Sanford, a former governor of South Carolina who recently ended his quixotic bid to challenge Mr. Trump for the Republican nomination.
“There’s a degree of political autonomy” that governors have, he added.
Mike DuHaime, a Republican strategist who advised former Gov. Chris Christie of New Jersey, put it more bluntly: “Many members of Congress are scared of the president’s ability to take them out in a primary — governors are less so.”
The examples have piled up over the last 18 months, as some of Mr. Trump’s aides have winced at how aggressively he wanted to participate in particular campaigns despite their urging him to stay out of those races.
For those candidates who won their governor’s races, their own political needs have since overshadowed those of Mr. Trump, and they have less incentive to fear him once elected.
In Florida, Mr. Trump’s aides helped save the flailing candidacy of Ron DeSantis in the 2018 Republican primary, and then the general election. Also last year, in Georgia, Mr. Trump helped pull Brian Kemp over the finish line in both the primary and the general election. In both cases, Mr. Trump’s advisers implored him to stay out of the primaries, and he agreed to — only to surprise his aides by jumping in to support Mr. DeSantis and Mr. Kemp.
Once that happened, Mr. Trump’s aides sought to make the best of it, trying to net victories in the states with an eye toward having allies there in 2020.
But since his election, Mr. DeSantis — once a congressman who frequently jabbed at Mr. Trump’s critics during the investigation by the special counsel, Robert S. Mueller III — has seemed fine bucking the president.
He has steered clear of public defenses of Mr. Trump, preferring not to spend his political capital by wading into national issues. He has indicated to reporters that he will be too busy to put much time toward helping Mr. Trump in his re-election battle.
And in a move that jolted Florida politics, the president’s campaign complied with a demand by Mr. DeSantis that Mr. Trump fire his own re-election campaign’s top Florida adviser, Susie Wiles, who has been credited with helping elect not only Mr. Trump in 2016 but also Mr. DeSantis in 2018.
Mr. DeSantis, who is seen as a possible Republican presidential candidate in 2024, viewed her as insufficiently loyal to him — and too close to another potential presidential candidate, former Gov. Rick Scott of Florida, whom she also helped elect, according to four people briefed on the events.
Her dismissal, in September, was agreed to by Mr. Trump and Brad Parscale, the president’s campaign manager, but the move infuriated a number of Trump advisers, who believe Ms. Wiles was an asset and who think the campaign should not have bent to a demand from a governor whom Mr. Trump assisted.
More recently, Mr. Trump was ignored by Mr. Kemp as the president pressed for an ally to fill the seat of Senator Johnny Isakson of Georgia, who is retiring at the end of the year. Mr. Trump favored Representative Doug Collins, an appointment that would have given him an additional loyalist in the Senate as an impeachment trial looms in that chamber.
But Mr. Kemp on Wednesday chose Kelly Loeffler, a business executive who he believes will not turn off the suburban women whose support he needs.
Mr. Kemp took Ms. Loeffler to meet Mr. Trump at the White House at a secret gathering two weeks ago, trying to reassure him. Mr. Trump did not budge — but neither did Mr. Kemp.
Even with Mr. DeSantis and Mr. Kemp walking a careful line with the president, Mr. Trump has seemed to relish playing kingmaker after getting a taste of it in 2018. So this year, he jumped into other races that offered him little benefit in his own re-election fight next year, or in Congress.
In Kentucky and Louisiana, where the Republican nominees for governor lost this year, the races were decided by a number of local factors, including negative perceptions of the incumbent Republican in Kentucky, Matt Bevin, and the moderate style of the incumbent Democrat in Louisiana, John Bel Edwards.
Still, Mr. Trump made heavily promoted visits to the states and touted the candidates on Twitter, personalizing the races almost every time he talked about them.
A loss would be damaging, Mr. Trump told the crowd at a rally in Kentucky the night before the election. “You can’t let that happen to me!” he implored.
Some of Mr. Trump’s advisers say they see fund-raising benefits in the president’s traveling to those states, even with the losses. And they believe that even if he had stayed out of the races, political reporters would have described them as losses for Mr. Trump.
But senior Republicans acknowledge that Mr. Trump still doesn’t understand the nuances between the types of races run by governors, who have to tend to voters back home, and senators and representatives, who must survive in Washington and have a different political balancing act.
Former Gov. Pat McCrory of North Carolina, a Republican, said that Mr. Trump shared something in common with his predecessor, Barack Obama, in that neither one had significant coattails in off-year elections. The two men developed a “personal relationship” with voters who turned out only for their presidential elections and could not be cajoled into supporting other candidates, he said.
Some Trump advisers have questioned why his aides have not pushed back more forcefully against his desire to inject himself into contests in solid-red states like Kentucky and Louisiana where there is no electoral benefit to him in 2020.
“The curse of Donald Trump is that he can’t help himself, and he always makes it about him,” Mr. Sanford said.