As President Trump ramps up his endorsements ahead of the 2024 primaries, he appears to be steering clear of taking a chance on outsider candidates in House races for now, despite having endorsed several outsiders for Senate.

Starting Tuesday evening, Mr. Trump released a list of 20 endorsements. So far this election season, Mr. Trump has endorsed about 30 House candidates, a fraction of the number he backed two years ago. Only three of those endorsed candidates are now running for open seats, and none of those seats is considered to be competitive.

In 2022, Mr. Trump endorsed nearly 150 House candidates and more than two dozen Senate candidates. Yet with most primaries still months away, there is plenty of time for Mr. Trump to flex his political muscle this cycle, if he intends to do so.

An analysis of the effects of Mr. Trump’s endorsement on a candidate’s electoral prospects published in the fall by a researcher at the University of Amsterdam, Michael Heseltine, found that since 2018, an endorsement from Mr. Trump was a boost — at least in GOP primaries.

“Across all election cycles, his endorsements produced little benefit for candidates in the general election,” Mr. Heseltine wrote. “However, endorsed candidates received a consistent and substantial electoral benefit in Republican primary elections, with these benefits growing marginally over time.”

Mr. Heseltine, though, found that the sort of candidates Mr. Trump endorsed changed after he left office. After exiting the White House, Mr. Heseltine writes, “partisan electoral goals were secondary to a strategic focus on retaining personal influence within the Republican party.”

The research also found that while Mr. Trump’s endorsement could lock up a primary, it could also hurt candidates in the general election.

“Endorsed candidates did not benefit financially and collectively received an aggregate vote share penalty of approximately 1.5 percentage points,” Mr. Heseltine wrote.

A political scientist at John Jay College, Brian Arbour, tells the Sun that he understands an endorsement from Mr. Trump to be worth about a 16-point boost, on average, in the Republican primary, saying, “It’s rare for something to be that valuable in a primary.”

Mr. Arbour says that in most races, a relatively small general election penalty is normally worth the trade-off for an individual candidate in order to lock up the Republican nomination. He pointed to Senator Vance’s 2022 campaign as an example.

“It’s not like it really matters — it didn’t hurt JD Vance enough,” Mr. Arbour says. “In Ohio, it’s a competitive race but we favor the Republican nominee whoever that is so getting to be the Republican nominee is quite valuable.”

Of Mr. Trump’s change in strategy, Mr. Arbour says his pivot toward prioritizing personal influence could serve two purposes. First, after leaving office he was attempting to maintain influence in the party. Second, after attempting to overturn the results of the 2020 election, loyalty became more important for Mr. Trump.

“Two ways to look at the difference between 2020 and 2022,” Mr. Arbour says. “In 2020 he’s the leader of the entire party and the incumbent president, and in 2022 he’s the leader of a faction of the party and trying to win the nomination in 2024.”

While Mr. Trump was relatively conservative in his endorsements this week, the former president has been bolder in his choices in GOP primary elections in the Senate.

In the Ohio Senate primary, Mr. Trump endorsed the least well-known candidate in the GOP field, the owner of a number of Ohio car dealerships and crypto businessman, Bernie Moreno, who also ran in 2022.

In endorsing Mr. Moreno, Mr. Trump snubbed Ohio’s secretary of state, Frank LaRose, a proven winner in statewide elections in Ohio, as well as a state senator, Matt Dolan.

In Montana, seen as one of the GOP’s best opportunities to flip a Senate seat in 2024, a scramble for endorsements is under way between businessman Tim Sheehy, who has touted endorsements from the likes of Senator Rubio and Congresswoman Marjorie Talyor Greene, and Congressman Matt Rosendale, who has teased a potential Senate bid in events in the state with Congressman Matt Gaetz.

Mr. Trump endorsed Mr. Rosendale in the 2018 Senate election in Montana, though Mr. Rosendale lost the general election against Senator Tester that year. 

In Arizona, Mr. Trump endorsed a devotee of his, a former TV news host, Kari Lake, in early October. Ms. Lake narrowly lost the Arizona gubernatorial race in 2022 to Governor Hobbs, who was criticized at the time for running an under-the-radar campaign. Ms. Lake does face a handful of challengers in the primary, with the most prominent being Sheriff Mark Lamb, though it’s not expected to be a competitive race.

In other competitive Senate races, like Pennsylvania, Republicans have been spared anxiety around a Trump endorsement because there are not competitive primaries.

In the Keystone State, the GOP’s favored candidate, David McCormick, is on a glide path to the nomination, after some familiar names from 2022, like the one-time GOP nominee for governor, Doug Mastriano, announced they would not run.

Mr. Mastriano’s failed gubernatorial bid in the 2022 Pennsylvania elections served as a cautionary tale regarding the effect Mr. Trump’s endorsements had on several races that year. In the GOP primary, Mr. Trump endorsed Mr. Mastriano, who was the most vocal candidate supporting Mr. Trump’s claims that the 2020 election was stolen.

By endorsing Mr. Mastriano, Mr. Trump pushed him to victory in the primary, defeating the GOP’s preferred candidate, Congressman Lou Barletta, who was seen as a stronger general election candidate. Mr. Mastriano then went on to suffer a 15-point landslide defeat to Governor Shapiro.

Mr. Mastriano wasn’t the only weak general election candidate Mr. Trump elevated in 2022. His endorsements in Senate races elevated Mehmet Oz in Pennsylvania, football star Herschel Walker in Georgia, and a retired brigadier general, Don Bolduc.

Mr. Trump’s office did not immediately respond to a request for comment from the Sun.