In the governor's race, Republican Nikki Haley faces Vincent Sheheen, who is trying to take the state's top post for Democrats after eight years of contention between Gov. Mark Sanford and the fellow Republicans who control both legislative chambers. If Haley wins, she would also be the state's first Indian-American governor.
Also on ballots is U.S. Sen. Jim DeMint, who is running for re-election against an unemployed military veteran, and candidates for the state's schools chief, lieutenant governor, top prosecutor and other statewide offices.
Polls open at 7 a.m. But voting already has been heavy as people cast absentee ballots at record levels for midterm elections.
Nearly 147,000 people had voted as of Monday, according to the state Election Commission. Nearly 10,000 more voters had requested absentee ballots but had yet to return them. They are due by 7 p.m. today. People could vote absentee in person at county election offices through 5 p.m. Monday.
The most recent high point for midterm absentee voting was 2006, when 75,651 ballots were cast as Sanford easily won a second term. Like most states, it has been higher in presidential contests. The record was 2008, when nearly 342,400 South Carolina residents voted absentee.
Commission spokesman Chris Whitmire credits the increase partly to better awareness, as the agency, candidates and parties made a point to educate residents on how to vote absentee.
"The other possibility is that voters are energized about voting in this election," he said. "If voters are excited about voting absentee, hopefully they're excited about voting on Election Day."
In congressional races, state House Rep. Tim Scott could become the first black Republican congressman from the Deep South since the 1800s. He faces Democrat Ben Frasier, a perennial candidate who is also black.
U.S. Rep. Joe Wilson is trying to keep his seat in what has become the costliest House race in state history. He faces Rob Miller, a former Marine captain, for the second time. Wilson's "You lie!" outburst last year as President Obama gave a health care speech to Congress sent cash pouring into both of their campaigns.
Incumbent U.S. Rep. John Spratt is seeking a 15th term in a tough re-election bid against state Sen. Mick Mulvaney. Spratt, the chairman of the House Budget Committee, is trying to hold on in a district that's become more Republican as parts of it became suburbs for Charlotte, N.C.
"It's probably the hardest fought of the 15 elections I've faced," Spratt said after rallying campaign workers this weekend.
On Monday, candidates were making a final push for voters.
Haley wrapped up a weeklong bus tour, and Sheheen flew around the state. Each ended the day with a rally.
Sheheen told a crowd of about 150 in a park gymnasium in Richland County that the election is about change and applauded heavy absentee voter turnout.
Haley also told about 300 supporters in Gilbert that "this is the time South Carolina's going to take our state back."
She was joined by all GOP nominees for statewide office, in addition to Wilson, DeMint and Sen. Lindsey Graham, state House Speaker Bobby Harrell, House Majority Leader Kenny Bingham, and outgoing Attorney General Henry McMaster. All spoke separately before Haley took the podium. Sanford also attended and got rounds of applause.
Republican nominees for other statewide offices traveled the state pushing for a GOP sweep. The only post now held by a Democrat is state schools chief. Superintendent Jim Rex decided to run for governor instead and lost in the primary.