Georgia’s two biggest races might not be decided in November.

An exclusive poll conducted this week for The Atlanta Journal-Constitution shows tight contests for governor and the U.S. Senate that are in danger of going to runoffs because no candidate gets more than 50 percent of the vote.

Libertarian candidates are taking a small but significant share, meaning no candidate holds the majority needed to win the general election.

In the governor’s race, 43 percent of likely voters — including voters who were leaning toward one candidate — back the Republican incumbent, Nathan Deal. Democrat Jason Carter holds 42 percent and Libertarian Andrew Hunt brings in 7 percent.

Perdue notched 45 percent, compared with 41 percent for Democrat Michelle Nunn and 6 percent for Libertarian Amanda Swafford, including leaners.

Among voters who have definitely selected a choice, Deal leads Carter, 42 percent to 40 percent; and Perdue leads Nunn, 44 percent to 38 percent.

“Libertarians in both races are siphoning off voters, probably from the Republican side, and you have the 50 percent threshold” for a victory, said Mark Schulman, the chief research officer at pollster Abt SRBI Inc. “So all of these races are highly competitive. The November election may amount to only round one, depending if the Libertarian vote melts away on Election Day.”

Historically, Libertarians perform better in pre-election polls than at the ballot box, when voters shift more to the two major parties. But at this point, Hunt and Swafford could be spoilers.

“Basically, I’ve given up on the Republicans and the Democrats all together,” said poll respondent Cindy Sutton, 51, of Kennesaw, who plans to vote Libertarian.

“Nobody is getting anything done and there needs to be some new blood in there,” Sutton said. “I like a lot of what Libertarians stand for. I don’t agree with everything, but that’s with any party.”

The poll’s margin of error is +/- 4 percentage points. The statewide poll of 884 likely voters was conducted Monday through Thursday by New York-based Abt SRBI Inc. with live calls to a mix of land-line and cellphones.