Republican Ed Gillespie, who narrowly lost his bid for U.S. Senate in 2014, faces a difficult effort to drum up grass-roots support for his run for governor of Virginia. (Kate Patterson/For The Washington Post)

Ed Gillespie, the consummate Republican insider as a former White House counselor, strategist and Karl Rove ally, managed to woo enough of his party’s balky right flank last year to win the GOP nomination for U.S. Senate.

Now, as he plans to run for governor in 2017, he will have to pull that off again. It could be a tall order.

Some Virginia Republicans have been clamoring for Gillespie to seek the governor’s mansion since last year, when the former Republican National Committee chairman came within an eyelash of toppling the seemingly indomitable Sen. Mark R. Warner (D).

But the GOP’s most conservative activists, who will play an outsize role if the party picks its nominee at a convention, still need convincing, interviews show. At a time when outsider candidates are upending presidential politics for both parties, grass-roots Republicans are not instantly embracing the notion of an insider for governor.

“Folks are not in the mood for that kind of politics these days,” said Chris Shores, who ran the campaign for Gillespie’s leading GOP Senate rival and now serves as statewide organizer for the presidential campaign of Sen. Ted Cruz (Tex.). “I don’t think that Donald Trump supporters, or Cruz supporters, or [Ben] Carson supporters are going to get behind Ed Gillespie in any way, shape or form.”

The mood of the grass roots could certainly shift between now and 2017, with state legislative races this year and the 2016 presidential race potentially leaving conservatives emboldened — or chastened. Either way, Gillespie will need their support if the GOP goes through with plans to pick its nominee at a convention — a day-long affair that draws only the most committed activists — rather than through a primary open to all voters.

A convention could be an especially tough forum for Gillespie if a conservative star such as former attorney general Ken Cuccinelli II gets into the race. Cuccinelli, who narrowly lost the 2013 governor’s race to Terry McAuliffe (D), said in recent days that he has not discounted making another run.

“Teiro and I have not ruled out running for governor in 2017, but we have barely begun to think about it,” Cuccinelli, referring to his wife, said Saturday in an e-mail to The Washington Post.

Gillespie won the Senate nomination at a convention — in Roanoke — with about 60 percent of the vote. Some supporters say convention-goers will be even more inclined to back him in the wake of his near-upset of Warner, a popular former governor who started the race 30 points up and outspent Gillespie 2 to 1.

“Ed Gillespie has shown a capacity to unite the Republican Party that has been exceedingly rare in Virginia over the last decade,” said Tucker Martin, an adviser to Gillespie’s Senate campaign. “He won the nomination last year in a convention, and he did that by reaching out to every segment of the Republican Party and running a big-tent campaign.”

Gillespie pulled that off last time with a tireless charm offensive, schlepping across the commonwealth for meetings big and small, sitting down with skeptics and asking for their votes face-to-face. They met a man who, yes, had been a senior adviser to Mitt Romney’s 2012 presidential campaign, but who also was an architect of Newt Gingrich’s 1994 “Contract With America.”

“Ed’s background is at the highest levels of national politics, but he hasn’t let that stop him from approaching politics in Virginia from the grass-roots angle,” said Steve Albertson, who runs the conservative Bull Elephant blog and has a leadership role in the party.

Since the Senate race, Gillespie has remained engaged, helping to raise money and rally voters for races — down to county supervisor and school board contests. On Thursday, Gillespie and his wife, Cathy, hosted a reception at their Fairfax County home for Jane Gandee, a candidate for supervisor there.

“I’ve had some people who have said they’ll do things for me, and now I can’t even get them to return a phone call,” Gandee said. “But not Ed and Cathy.”

Anthony Stacy said it has been “invaluable” to his Fairfax County School Board bid to have the moral support and guidance of the onetime White House counselor, who worked for President George W. Bush.

Gillespie’s continued involvement had stoked rumors that he was eyeing the governor’s mansion. There had been talk of that from the time Gillespie took on Warner for what initially looked like a hopeless — but recognition-boosting — task. Gillespie brushed off that notion during the Senate campaign and even after, as a close friend and political ally, state Sen. Mark D. Obenshain (R-Rockingham), began running for governor.

Obenshain had been widely seen as the favorite to win the 2017 nomination for governor, after narrowly losing the 2013 race for attorney general.

Gillespie told those who encouraged him to run for governor that he would not do so as long as Obenshain was in the race. In a surprise move Monday, Obenshain bowed out. Word leaked that day that Gillespie was in, though he stayed mum. On Friday, Gillespie confirmed it.

“I’ll start laying a foundation to run myself after our elections here are over next month,” Gillespie said Friday in an e-mail to The Post.

Obenshain said that no one pushed him out; he simply concluded that he was not up for another statewide run in 2017. But the news was welcomed by many party insiders, who deeply respected Obenshain but saw that Gillespie was a stronger candidate because of his speaking skills and his ability, as a former RNC chief, to raise big money.

But that feeling was not universal. Some conservatives who were skeptical of Gillespie as a Senate nominee said that they only soured on him as that race unfolded.

They wished that he had been more of a bomb thrower. John Fredericks, host of a popular conservative talk radio show, called Gillespie’s 2014 campaign “vanilla.” That approach won’t satisfy callers to his show, who are drawn to the in-your-face messaging from Trump and other outsiders on the national stage, Fredericks said.

“They’ve lost confidence in the political class to get anything meaningful done,” he said. “Ed Gillespie is the Virginia caricature of Jeb Bush. If you’re excited about the Jeb Bush candidacy nationally and in Virginia, then you’re going to be really fired up about Ed. If not, then you’re not.”

Some of Gillespie’s establishment supporters, however, remain impressed with his near-win and expressed confidence that the party will unite behind him.

“He still has the halo after his close loss to Warner,” said Richard Cullen, a former Virginia attorney general who is chairman of McGuireWoods, the Richmond-based legal and lobbying powerhouse. “We’re hungry for a win and I think the appetite to win is going to be greater than any parochial division.”

Gillespie’s success at a 2017 convention probably will depend on the level of competition and the attitude of the electorate, political strategists said. In 2014, when Warner looked unbeatable, not many Republicans were itching to take him on. Gillespie’s nearest rival, retired Air Force pilot Shak Hill, had little money or name recognition.

Republicans also were coming off a Democratic sweep in the 2013 races for governor, lieutenant governor and attorney general. That made some conservatives open to Gillespie as a more pragmatic choice than Hill.

Daniel Bradshaw, the immediate past chair of the Prince Edward County Republican Party, said that Gillespie’s success with the grass roots will depend on who else is out there.

Right now, Gillespie is the only Republican in the race. Among Democrats, Lt. Gov. Ralph Northam is the only declared candidate. Among Republicans mentioned as potential candidates are: Cuccinelli; Rep. Rob Wittman; Northern Virginia technology entrepreneur Pete Snyder; Corey Stewart, chairman of the Prince William Board of Supervisors; and state Sens. William M. Stanley Jr. of Franklin, Jeffrey L. McWaters of Virginia Beach and Thomas A. Garrett Jr. of Buckingham.

“Gillespie is definitely not a huge favorite among the conservative grass roots of the party,” said Bradshaw, who was political director for E.W. Jackson, the Chesapeake minister who won the 2013 nomination for lieutenant governor in an upset. “But it remains to be seen who all gets in.”