Sabato, however, finds it unlikely that this year will see a repeat of such an upset.

“Everyone points to Jackson’s unexpected victory at the 2013 convention to say that conventions can do very unusual things. True enough, but there was a large field for lieutenant governor and no obvious favorite — and the GOP hadn’t yet lost every statewide elected post. There’s a learning curve here, and it isn’t flat,” he said.

Whether Gillespie will get the support of the tea party faction of the GOP remains to be seen, Sabato said.

“In a perfect world for the tea party, Gillespie wouldn’t be their first pick, or their second or third. He’s been a D.C. lobbyist and establishment figure for a long time. My guess is they’ll be split. (But) as long as Gillespie is seen as the only credible general-election challenger, he’ll make it through the convention.”

But the key question, Sabato said, is: Will the three minor candidates be able to push Gillespie further to the right, making him less electable in November?

Warner’s campaign is gearing up to counter any challenger, touting his ability to work across the aisle and painting him as a moderate, centrist candidate.