In response to the Dominion question, Mr. Youngkin said, “Ladies and gentlemen, this is the most important issue we’re going to talk about right now.” He laid out “five steps to restore our trust” in elections.
A former co-chief executive of the Carlyle Group, Mr. Youngkin has spent at least $5.5 million of his own money on the race. Part of his appeal to Republicans is that in the general election, he could theoretically match the spending of the leading Democrat, former Gov. Terry McAuliffe.
Polls show that Mr. McAuliffe, with the advantage of name recognition from an earlier term, has a hefty lead over three Democratic rivals going into their party primary on June 8.
To many observers, it was the 2013 race won by Mr. McAuliffe that began the rout of Virginia Republicans. Ahead of that election, social conservatives gained control of the G.O.P. central committee, canceled a primary and chose one of their own, Kenneth T. Cuccinelli II, at a Tea Party-flavored convention.
Mr. Cuccinelli lost to Mr. McAuliffe, a Democratic fund-raiser and friend of Hillary and Bill Clinton’s — thus beginning Republicans’ years in the wilderness.
“That’s a direct result of the Cuccinelli heist, if you will,” said Chris Peace, a Republican former state lawmaker. “Much of the old guard, the center-right of the party, was pushed out.”
Four years later, the party’s nominee for governor in 2017, Ed Gillespie, lost decisively after making a Trumpian effort to stir fear of crimes committed by undocumented immigrants. The next year, the party’s Senate nominee, Corey Stewart, ran on preserving Confederate statues — and lost in a landslide.