COLUMBIA, S.C. - Republican U.S. Senate candidates Jim DeMint and David Beasley spent the final hours before polls open Tuesday shaking voters' hands in whirlwind tours across the state and squeezing in one last radio debate.

Beasley, a former governor, and DeMint, a three-term congressman, have been in a two-man battle since they emerged from the six-way June 8 primary as the top vote-getters. Since neither got more than 50 percent, a runoff was scheduled and the candidates dashed out of the gate to grab every vote.

The winner of Tuesday's runoff will face Democrat Inez Tenenbaum in the general election to replace retiring Sen. Ernest "Fritz" Hollings.

Political observers say voter turnout will be key, especially in the Lowcountry, which is up for grabs. The two former GOP Senate candidates from that area have endorsed DeMint, who is from Greenville.

"I think the better the turnout, the better off I am," said DeMint.

Francis Marion University political scientist Neal Thigpen said DeMint can't afford to have voters stay home because Beasley's supporters "are passionate for him" and "probably would be more inclined to come back out a second time."

Beasley has strong support in his home region of the Pee Dee and in the Upstate.

His eyes were blood-shot, but Beasley still flashed that familiar smile as he talked about staying up all night Sunday and most of Monday to campaign.

"I want the voters to know David Beasley is going to work around the clock," said Beasley, who got one hour of sleep between meeting with voters in Charleston, Columbia, Florence, Spartanburg and Sumter.

DeMint called Beasley's last-minute hopscotch "a sign of desperation."

"They're scrambling around," said DeMint, who added he's covered more ground in the past three days.

Their paths crossed Monday afternoon at Columbia radio station WVOC-AM for an hourlong, commercial-free debate.

Beasley touted his experience creating jobs and reforming state government while governor. DeMint talked about his work in Congress the past six years.

The two conservative candidates mostly sparred over U.S. trade policies, the biggest difference between them.

Beasley attacked DeMint for voting to "sell out" South Carolina and send jobs overseas and give the state one of the worst unemployment rates in the country.

"It's because you have not stood up with the rest of our congressional delegation to fight for South Carolina jobs," Beasley said. "We have unfair foreign trade taking place."

DeMint said his position on free trade has helped create jobs in the state and open more opportunities for South Carolina businesses.

The intensity of their grueling campaign schedules were apparent at one point as they interrupted each other, shooting statistics back and forth to prove their points. They talked over each other in loud voices and had to be quieted by the debate's host.

Both accused each other of lobbing attacks in what was supposed to be a cordial campaign. DeMint said Beasley was misleading voters, while Beasley accused DeMint of unleashing a "character assassination on me."