Virginia gubernatorial candidate Robert Sarvis answers questions and meets with students at South County High School during a Meet the Candidates' Day on Sept. 27 in Lorton, Va. (Evy Mages/For The Washington Post)

The fate of a third-party candidate in the Virginia governor’s race — and even the result on Election Day — could rest on a fraction of a percentage point on a political Web site.

On Oct. 24, Ken Cuccinelli II (R) and businessman Terry McAuliffe (D) are expected to clash at Virginia Tech’s Blacksburg campus for their final debate of the contest. It’s not clear whether they will be joined on stage by the race’s wild card: Libertarian Robert Sarvis.

With McAuliffe and Cuccinelli engaged in a mostly negative race, multiple surveys have shown Sarvis doing far better than third-party candidates typically fare in Virginia. He appears to be pulling the majority of his votes from Cuccinelli, the state’s attorney general, who has consistently trailed McAuliffe in recent months.

Under the rules negotiated by Cuccinelli, McAuliffe and the debate’s sponsor — WDBJ (Channel 7), the Roanoke CBS affiliate — Sarvis can participate in the debate if he is “polling at 10 percent or above” as of Oct. 10. A handful of recent surveys — including a Washington Post/Abt-SRBI poll in September — have shown Sarvis cracking double digits, but several others have not.

This isn’t just a math problem. The question of which polls to include in the debate calculus has been the subject of much behind-the-scenes wrangling, although most of the players involved don’t want to talk about it.

Cuccinelli has little motivation to grant Sarvis the stature and free airtime that come with a debate, and people involved in the talks said Cuccinelli’s campaign has consistently sought to make it harder for Sarvis to get in.

Cuccinelli spokesman Richard Cullen declined to wade into the details of the discussion. “We’re going to let the process play itself out based on the rules that both campaigns agreed upon,” Cullen said.

Publicly, Cuccinelli’s team has made it clear what it thinks of Sarvis’s candidacy. “Voting for Sarvis is essentially throwing your vote away,” Cuccinelli adviser Chris LaCivita previously told The Washington Post.

Although Sarvis has criticized both candidates, McAuliffe has not fired back.

“We agreed to the debate rules last week, including a reasonable standard for the inclusion of third-party candidates,” McAuliffe spokesman Josh Schwerin said. “While the Cuccinelli campaign has expressed concern to us about including Mr. Sarvis in the debate, we feel that if he meets the threshold, he should be included.”

Sarvis is optimistic.

“There’s a very good chance I’ll be in that debate,” Sarvis said after a forum Sunday in Annandale.

The debate agreement originally said Sarvis needed to be “polling at 10 percent or above in major independent statewide polls” but did not specify what that meant. Cuccinelli’s camp always wanted a higher number, sources said. Presidential debates typically set a threshold of 15 percent for third-party candidates.

More recently, as Sarvis’s stock rose, the McAuliffe and Cuccinelli campaigns and WDBJ agreed to new language saying that the decision would “rely heavily on the averages of major polls as listed on RealClearPolitics,” a nonpartisan site that aggregates poll results, as well as surveys released in the final three weeks before Oct. 10.

On Tuesday alone, three new tallies of the governor’s race were released. A Politico poll — conducted by Public Policy Polling and Harper Polling, which use autodial technology — put Sarvis at 12 percent among likely voters. A Christopher Newport University survey gave Sarvis 8 percent, and a Roanoke College poll had him at 9 percent. McAuliffe led all three polls.

As of Tuesday afternoon, Sarvis’s RealClearPolitics average stood at 9.1 percent.

Does that mean he is falling short? The final decision is up to WDBJ. The station’s news director, Kelly Zuber, would not comment on whether she had been lobbied on the Sarvis issue.

Zuber told the Washington Examiner last month that Cuccinelli’s campaign had asked “several questions” about the debate rules, including one “about raising the polling percentage for the third-party candidate.”

The debate language says WDBJ will decide “in consultation with” Roanoke College Professor Harry Wilson and Virginia Tech Professor Robert Denton. Wilson and Denton declined to comment on the talks and deferred to Zuber.

Until Thursday, when the issue presumably will be decided, the debate is in an odd state of flux. The debate is widely expected to happen, but the official notice and news release have not gone out, even though it is just two weeks away.

Sarvis has raised only a fraction of the cash that McAuliffe and Cuccinelli have, so he’s had a much harder time getting his message out.

A debate would give him his biggest platform yet, even as it remains unclear how much support he really has.

In the CNU poll released Tuesday, less than half of the likely voters who picked Sarvis said their decision was “very firm,” while McAuliffe and Cuccinelli backers said they were far more certain of their choice.

While he wouldn’t discuss the debate negotiations, Denton said he would be keeping a close eye on Sarvis’s numbers until Nov. 5.

“In reality, as you get closer to Election Day, independent support historically tends to erode,” Denton said.

“Ten percent is pretty good in Virginia.”