Three weeks, two candidates, one nomination and very little room for error: Those were the facts and figures facing Democrats Vernon Jones and Jim Martin as Phase 2 of the U.S. Senate race began Wednesday.

Jones, the DeKalb County CEO, was the top vote-getter in Tuesday's five-way primary, with former lawmaker Martin finishing second. About 29,000 votes separated the two, with Jones collecting about 40 percent of the vote to 34 percent for Martin.

But those numbers must now be set aside, because there's one that looms larger now, and that's voter turnout.

There were about 480,000 votes cast in Tuesday's primary, a quarter fewer than were cast in the 2004 Democratic Senate primary. Persuading voters to come back to the polls in three weeks must be the candidates' top priority.

But good luck with that.

Turnout in runoffs is historically dismal. Martin knows this well. In 2006 he finished first in a five-person primary for the Democratic nomination as lieutenant governor. He won 41 percent of the nearly 450,000 votes cast in the primary. He captured the nomination by taking 62 percent of the 225,000 votes cast in the runoff.

And historically, the top vote getter in a primary wins the runoff 70 percent of the time, said University of Georgia political scientist Charles Bullock, who has authored a book about runoff elections.

But don't tell Martin that.

"It's a different race at this point because you're able to present a much clearer choice," said Martin's campaign manager Ellery Gould.

Jones and Martin both stayed largely out of the public eye on Wednesday as their campaigns regrouped. A key ingredient in their strategy will be cash. Money offers a particularly big advantage in a compressed campaign when underfunded candidates are less able to count on media coverage or grass roots campaigning.

As of June 30, Martin had $330,000 cash on hand, nearly twice what Jones reported to the Federal Election Commission. But the final two weeks of the primary was expensive.

"We spent a lot of money, but we think can raise a lot of money," Gould said. "I'm not putting a number on it, but I think we can do what we need to do."

Jones said in an e-mail ("yes, absolutely!") that he'd have enough money left to be competitive in the runoff and run campaign ads on TV.

Both men have challenges ahead.

For Martin, it's finding a way to vault from second to first and persuade his primary voters to return on Aug. 5. And while he picked up the endorsement of third-place finisher Dale Cardwell on Wednesday, those types of nods don't always make a difference, Bullock said.

"Voters are not sheep who can be that easily led by a person saying, 'I'm out of it, and I endorse such and such,'" Bullock said.

Still, he said, Martin would "probably as soon have the endorsement as not. But there's no guarantee."

Rand Knight and Josh Lanier, who finished fourth and fifth, respectively, could not be reached for comment on Wednesday.

For Jones the challenge is close to home. While he was the leading vote-getter in DeKalb County, he did not claim a majority of the votes in a county that elected him three times as its CEO.

Of the 70,000-plus votes cast in DeKalb, about 40,000 went to someone other than Jones.

"That was really telling for Vernon," Bullock said. "Those who knew him best gave him very mixed results."

But Jones seemed unconcerned Wednesday.

"DeKalb County is the best-managed county in the state of Georgia," Jones said in the e-mail.

Martin's campaign noticed the DeKalb results.

"If we can do well in DeKalb, that says we can do well any where," Gould said. "We have friends there, and as of this morning we have more."

Waiting on the other side of the runoff is a rested and well-funded Republican incumbent in U.S. Sen. Saxby Chambliss. Libertarian nominee Allen Buckley is also on the ballot.

"I do congratulate all five of those [Democrats] for running good, strong races," Chambliss said on Wednesday. "Whoever comes out of that runoff is going to be a formidable opponent and we'll have about 90 days of head-to-head combat and dialogue on the issues.

"But, I don't have a preference. We'll have a stark contrast between their position and mine."