A close Virginia gubernatorial primary that saw a fervent supporter of President Trump nearly upset a well-funded and organized Republican establishment candidate is being seen as a sign that Trump's support could put some incumbent Republicans in jeopardy.

Former Republican National Committee Chairman Ed Gillespie barely beat Prince William County Chairman Corey Stewart Tuesday by a little over 1 percentage point, a victory margin of just 4,323 votes out of 366,114 cast. Polls and GOP politicos had predicted that the establishment-backed Gillespie would win in a rout.

Now there are worries that Gillespie will struggle to motivate hardcore Trump supporters to turn out for him in southern parts of the state this November and at the same time will face hostile liberal voters in the Northern Virginia suburbs of Washington, D.C.

That would be bad enough for Republican prospects in Virginia this year and in similar races across the country in 2018. But Stewart's unexpectedly strong showing also revives the possibility of Republican incumbents facing pro-Trump primary challengers, with or without the president's blessing, with the GOP majority in the House on the line.

"I think Corey's strong showing should be yet another wake-up call to the Republican establishment," said Chris Barron, a Virginia-based conservative operative who is supportive of the president. "The establishment might not like Trump, but the grassroots loves him. This is not their Republican Party anymore; it is his."

Another Republican consultant described a "double squeeze" in which GOP incumbents face both a surge of motivated anti-Trump voters in the general election, but first have to deal with a primary electorate dominated by voters who wonder when the party's congressional wing is going to start backing Trump. While the first group gets the most media attention, the consultant said, the second is angry that Capitol Hill Republicans haven't delivered on things like the border wall.

Past Trump imitators have not fared as well in Republican primaries as the president himself. House Speaker Paul Ryan, R-Wis., defeated businessman Paul Nehlen in an 84-16 landslide last year. Sen. Marco Rubio, R-Fla., dispatched self-funding millionaire developer Carlos Beruff 71-19 after deciding to seek a second term.

Neither challenger had Trump's endorsement. In both cases, he at least nominally supported the incumbent, though Nehlen did receive a Trump Twitter shout-out. But these defeated candidates seemed to expose the limits of running like Trump without the future president's unique political talents, fame or vast earned media advantage.

In Virginia, Stewart wasn't endorsed by Trump either. He was fired as Trump's state campaign chairman because his protest against "establishment pukes" at the Republican National Committee went too far even for the most combative and unconventional major-party presidential nominee in recent memory.

None of this stopped Stewart from winning big in Trump Country. In Southwest Virginia, Trump's stronghold in the state, Stewart more than doubled Gillespie's support, and he received more votes than both Democrat candidates combined (though 177,000 more Democrats voted than Republicans statewide).

This showing may embolden Trump-friendly Republican primary candidates elsewhere. Kelli Ward, a GOP state senator who lost a primary bid against Sen. John McCain, R-Ariz., last year, appears to be gearing up for a challenge to Sen. Jeff Flake, R-Ariz., in 2018.

In Tennessee, Republican state Sen. Mae Beavers linked herself to Trump when she announced last month that she was running for governor. "President Donald J. Trump is taking the lead in Washington, D.C., to 'drain the swamp' there, but we have our own swamp in Tennessee and I intend to do the same thing in the Volunteer State," she said in a statement.

Gillespie won the Virginia GOP primary by beating Stewart by a 2-1 margin in Arlington and Alexandria. He also carried Richmond and its suburbs. He beat Stewart 48-39 in vote-rich Fairfax County. These were mainly areas that voted against Trump in last year's Republican primary and the general election against Hillary Clinton.

"Ed Gillespie ran a primary campaign that was focused on what he was going to do as governor," said Chris LaCivita, a Virginia-based Republican strategist. "It was positive, issue-focused and never once in any paid media attacked Corey Stewart. That will serve him well as the general election gets underway."

"That being said, it was obvious that in pursuing a strategy which had to be based on internal numbers, the campaign was operating under the assumption that it could take the risk," LaCivita added. "Its surveys clearly missed the mark — and this should serve as a classic lesson for future campaigns that no matter the advantage you may hold over your opponent, if you ignore their constant attacks (as Ed did on Corey) and do not respond and set the record straight, you're playing with fire."

Republicans may be playing with fire in Virginia, where the "double squeeze" certainly holds. It will be hard for Gillespie to win without those southwest Trump-Stewart voters turning out in big numbers. At the same time, 59 percent of Virginians polled by the Washington Post and ABC News said they disapproved of Trump's performance in office.

It is a circle Trump supporters maintain Republicans are going to have to square.

"The base — at least in Virginia, and I suspect elsewhere — is fiercely loyal to President Trump," Barron said. "Incumbents, like [Virginia Rep.] Barbara Comstock, who have made it a point to distance themselves from the president do so at their own electoral peril."