President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE has solidified his grip on the Republican Party, forcing GOP lawmakers to think twice about challenging him in public for fear that it might come back to hurt them politically.

Rep. Mark Sanford Mark SanfordOn The Money: Business world braces for blue sweep | Federal Reserve chief to outline plans for inflation, economy | Meadows 'not optimistic' about stalemate on coronavirus deal Trump critic Sanford forms anti-debt advocacy group Republicans officially renominate Trump for president MORE's (R-S.C.) loss in Tuesday’s primary is the latest reminder to Republicans of the president's popularity with the GOP base and his ability to inflict revenge when angered.

ADVERTISEMENT

Trump ripped Sanford and offered support to his GOP rival on Twitter just hours before Sanford’s primary loss, as voters continued to go to the polls.

The message to Republicans was unmistakable: Trump will get involved in your primary if you cross him.

On Wednesday, some predicted Republicans will be even more afraid to go after Trump after what happened to Sanford.

“Most already are,” added Rep. Ryan Costello Ryan Anthony CostellloTrump struggles to stay on script, frustrating GOP again Bottom line Former GOP Rep. Costello launches lobbying shop MORE (R-Pa.), an outspoken Trump critic who is retiring from Congress.

One Republican senator who requested anonymity to discuss feelings about Trump within the conference candidly said colleagues know that if they go after the president, they are likely to hear about it publicly.

“He will not take a punch, he responds every time,” the senator said, adding: “I will not make comments about the president.”

The fear of taking Trump on was evident when the president visited the Senate GOP lunch last month amid deep angst over the tariffs being imposed in imports of steel and aluminum.

Despite widespread anger over those tariffs, not a single GOP senator raised the issue with Trump during the meeting.

GOP lawmakers say there is a strong reluctance to clash with the president because he could pay them back by thwarting their legislative priorities or drumming up opposition among Republican base voters.

Sen. Pat Roberts Charles (Pat) Patrick RobertsThe Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill GOP senators say coronavirus deal dead until after election MORE (R-Kan.), chairman of the Agriculture, Nutrition and Forestry Committee, vehemently disagrees with Trump’s use of tariffs, but he said last week that he had concerns about backing a measure sponsored by Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (R-Tenn.) to curtail Trump’s use of tariffs for fear it would imperil the farm bill.

“I don't want to rile the waters ... I don't think the president will be very pleased,” he told reporters last week.

Some Republicans, such as Sanford, have repeatedly criticized Trump. But most of them are retiring.

One such lawmaker, Corker, drew attention on Wednesday by comparing his colleagues to members of a cult.

“It’s becoming a cultish thing, isn’t it?” Corker said Wednesday, a day after he mocked fellow Republicans for being afraid of poking the president. “And it’s not a good place for any party to end up with a cult-like situation as it relates to a president that happens to be of — purportedly — of the same party.”

Sanford wasn’t the first Republican to suffer politically after a battle with Trump.

Rep. Martha Roby Martha Dubina RobyBarry Moore wins Alabama GOP runoff to replace Martha Roby The 14 other key races to watch on Super Tuesday Collins Senate bid sets off game of musical chairs for GOP MORE (R-Ala.) was forced into a runoff earlier this month after disavowing Trump in the 2016 presidential contest.

Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeHow fast population growth made Arizona a swing state Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden MORE (R-Ariz.) is one of the most aggressive GOP Trump critics. He is not running for reelection after polls suggested he would not win.

Costello said criticizing Trump opens you up to attacks in a primary.

“In a primary, if you’re going to provide any level of questioning or critique of the president in any way, you are obviously opening yourself up to have someone say that you’re ‘not supporting the president,’ ” Costello told The Hill. “You’re going to get some grief.”

Trump allies say that is a strength of the president’s — and something GOP lawmakers and other Republican office holders should keep in mind.

"President Trump is one of … the most popular presidents with Republicans in history,” said Rep. Chris Collins Christopher (Chris) Carl CollinsConspicuous by their absence from the Republican Convention NY Republican Chris Jacobs wins special election to replace Chris Collins 5 things to watch in Tuesday's primaries MORE (R-N.Y.), a Trump ally.

“If you’re not on the same page as the president, and 85-90 percent of your base is, you can see where that can cause a problem,” Collins said.

There have been questions about whether Trump will see a primary challenge in 2020, though his power in primaries could make Republicans less likely to give air to a GOP challenger.

There’s also a link to the probe by special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE.

GOP leaders have been firm in arguing that Mueller should be allowed to continue his probe even as the White House and its allies have increased their attacks on the investigation.

As Trump’s grip on his party tightens, it’s possible that could change.

A new Morning Consult-Politico poll on Wednesday showed 36 percent of respondents now have a negative impression of Mueller’s investigation, a 13-point jump from last summer.

Other Republicans said the main takeaway from Tuesday’s primary results is that if lawmakers want Trump’s support, they need to back his agenda.

“I don’t know that it sends a message you shouldn’t cross [Trump]. It sends a message that he’s certainly interested in those who want to help support his agenda,” said Rep. Roger Williams John (Roger) Roger WilliamsThe Hill's 12:30 Report - Presented by Facebook - Yoho apologizes for accosting AOC Ocasio-Cortez accosted by GOP lawmaker over remarks: 'That kind of confrontation hasn't ever happened to me' Cook shifts 20 House districts toward Democrats MORE (R-Texas).

But Flake said Tuesday’s primary results underscored the president’s power.

“This is Trump’s party,” he said. “It was reiterated last night. If you want to win a Republican primary, you can’t deviate much from the script, the president’s script. You can’t criticize policies or behavior.”

Asked later if his colleagues are scared of facing the president’s wrath, Flake said, “yes.”

Jordain Carney contributed.