Rep. Alex X. Mooney pummeled Rep. David B. McKinley by over 18 percentage points in the GOP primary for West Virginia’s redrawn 2nd District, an outcome that did not surprise their colleagues, who know how crucial an endorsement from former President Donald Trump can be for Republican candidates.

Just days before Tuesday’s primary, Mooney joined Rep. Mike Kelly, R-Pa., and other congressional candidates with the former president’s backing for a Trump rally in Greensburg, Pa., a little more than an hour from Mooney’s district. Kelly was struck by the eagerness and resilience rallygoers had to see Trump speak despite hours of waiting and constant rainfall.

“But I watched those people getting there at 11 o’clock in the morning in a pouring rain and standing there all day waiting to hear him talk — that’s hard to do,” Kelly said of Trump’s ability to command a crowd.

Mooney was not the only out-of-state candidate there. J.D. Vance, who recently won the primary for an open Senate seat in Ohio with the support of Trump, also spoke at the event.

“The president still wields such great influence,” Kelly said.

Mooney and McKinley were forced into a primary fight after the state lost one of its seats in reapportionment. The race had the potential to favor McKinley because, under the new congressional map, around 66 percent of voters came from his old district compared to 33 percent from Mooney’s old district. 

Trump’s backing does not make a candidate invincible. In Tuesday’s Republican primary for governor of Nebraska, for example, his endorsed candidate, Charles Herbster, finished almost 4 points behind nominee Jim Pillen.

But no one in the House GOP Conference was talking about that Wednesday.

Rep. Ronny Jackson, R-Texas, used to work as Trump’s physician in the White House and threw his support behind Mooney in the primary.

“Trump’s endorsement probably made the difference there. I mean, I really do. I think without it, it would have been a tight race,” Jackson said.

And though McKinley voted with Trump more than Mooney did (91.1 percent for McKinley compared to 86.4 percent for Mooney), two votes proved to be more consequential: McKinley’s vote for a bipartisan infrastructure package that provided significant funding for West Virginia’s roads and bridges, and his vote for a 9/11-style commission to investigate the Jan. 6, 2021, Capitol attack. Trump endorsed Mooney the day President Joe Biden signed the infrastructure bill into law.

Mooney’s ads honed in on these two votes, saying McKinley, a seventh-generation West Virginian, “betrayed” the state.

Ultimately, Mooney won decisively, with 54.2 percent of the vote to McKinley’s 35.6 percent. The nominee is heavily favored in November in a state Trump carried with 68 percent of the vote in 2020.

“It was a convincing win, and it just goes to show how substantial the Trump endorsement is,” Rep. Jim Banks, chairman of the Republican Study Committee, said. “There is no endorsement that’s more sought after in politics today than Donald Trump’s endorsement, and that race is a good example of why.”

Banks noted the differences between Mooney and McKinley were evident. Banks said Mooney had a “solid, America first, pro-Trump voting record” and McKinley “didn’t.”

In Ohio, Trump’s endorsement of Vance weeks before the primary propelled him past competitors, setting him up for a general election contest with Rep. Tim Ryan, D-Ohio, for the seat being given up by Republican Sen. Rob Portman. 

“There’s not a Republican in this country that has a stronger endorsement,”  Rep. Jason Smith, R-Mo., said.

With an open Senate seat in his state, and two of his House colleagues — Reps. Vicky Hartzler and Billy Long — among a crowd of candidates vying for the nomination, Smith said that “whoever Trump endorses in the Missouri Senate race will win.”

Rep. Scott Perry, R-Pa., chairman of the hard-line House Freedom Caucus, of which Mooney is a member, didn’t attribute all of Mooney’s win to Trump’s endorsement but said it “sure doesn’t hurt.”

“What really tipped the scales was how Alex votes and how he represents his constituents, his bosses and how the other guy came up here and represented Washington, D.C. That’s what really tipped the scales,” Perry said.

Rep. Lauren Boebert, who, like Jackson, endorsed Mooney, said the endorsement helped, but she attributed the win more to Mooney’s values.

“The Trump endorsement always helps, but Alex Mooney is a true conservative, and that’s why he won,” the Colorado Republican said.

In November, Mooney predicted Trump’s blessing would be the nail in the coffin for McKinley when he said the endorsement would make it “basically impossible” for McKinley to win.

Mooney said on Twitter that Trump congratulated him on the victory and that he thanked Trump for the support.

What’s clear is that any Republican running without Trump’s backing is in for an uphill battle or worse.

“I think it’s more than uphill. They got to climb a steep mountain,” Kelly said.

Minority Whip Steve Scalise said he is glad the primary is over.

“Alex and David are both good friends, and Alex won last night, and I think probably for the whole delegation in our conference, we’re glad that’s over,” the Louisiana Republican said. “You don’t ever want to have to go through a member-on-member race.”

There are still two ethics investigations into Mooney that concern his campaign spending and whether he tampered with a previous inquiry. The House Ethics Committee said it will make a public announcement about its course of action no later than May 23.

Representatives for Mooney and McKinley did not respond to requests for comment.