COLUMBIA - U.S. Sen. Lindsey Graham headlines primary election ballots on Tuesday in South Carolina, where officials were keeping an eye on hot weather that could affect turnout and voting machines.

State Election Commission spokesman Chris Whitmire said the weather might be a factor because not all the state's polling places are air conditioned. With temperatures expected to approach triple digits, he said people should vote early and take precautions in the heat.

The hot weather was one of the reasons Mr. Graham and his Republican challenger, Buddy Witherspoon, were burning up phone lines during get-out-the-vote efforts Monday.

"School is out, vacations have begun and temperatures are very high," said Mr. Witherspoon, a 69-year-old retired orthodontist, after a day of interviews and shaking hands .

Mr. Graham stopped by his Columbia headquarters, where volunteers were working their way through lists of voters, and Mr. Graham picked up a cell phone to call voters himself. Campaign manager Scott Farmer said they'd made 40,000 calls heading into today.

Two Democratic newcomers to South Carolina politics - Michael Cone and Bob Conley - are facing off to run against the winner of the Graham-Witherspooon contest.

Voters also will choose U.S. House nominees and names for the ballots in the 48 state House and 22 state Senate contests, in addition to other local races.

Poll workers will have to keep an eye on voting machines that have been known to overheat. Mr. Whitmire said the machines have an upper-operating temperature range of 95 degrees and shut down to protect voter data when they get too hot.

That happens rarely and when they're restarted, the vote tallies are intact.

The state Election Commission reported more than 2.3 million were registered to vote - up by 94,000 from January's presidential primaries.

But no one was expecting turnout to match the 44 percent of registered voters who came out five months ago.

Absentee voting is one sign of that: While more than 64,000 absentee ballots were requested in January, only about 38,000 have been requested for Tuesday's primary, Mr. Whitmire said.

Democrats were expecting lower turnout than in January, when presidential candidates "were spending millions to get people to the polls," said Joe Werner, the state party's executive director.