WASHINGTON — Election Day will be something of an afterthought for tens of millions of Americans — they’ll be voting well ahead of time.

In fact, six weeks out from Election Day, some voters in Kentucky, South Carolina and Virginia already are done.

Nationwide, about a third of the electorate is expected to vote early this year, thanks to expanded early voting provisions and fewer restrictions on absentee voting, researchers project. In all, more than 30 states allow any registered voter to cast an early ballot, some in person and others by mail.

Greg Dearing, of Louisville, Ky., locked in his ballot for Barack Obama on Thursday.

“I’m usually a straight party voter,” said Dearing, who will be vacationing in California on Nov. 4. “It would take something very far-fetched to make me regret my vote.”

Early voting has been on the increase in recent years: In 2004, 22 percent of voters cast an early presidential ballot; in 2000, 16 percent voted early.

A longer home stretch

It’s a trend that is fundamentally changing the home stretch of American political campaigns. October surprises? They’d better come in September if campaigns want to influence every vote. Get- out-the-vote operations? They’re already under way in some states.

“You can’t hold your big guns right to the end,” said Paul Gronke, director of the Early Voting Information Center at Reed College in Oregon. “When up to 25 or 30 percent of the electorate has already cast a ballot, it might not be wise to wait until the last minute” to make a game-changing play for votes.

Even the presidential debate series, which begins Friday and runs through Oct. 15, will come after many have voted. However, experts say the earliest voters tend to be party loyalists who wouldn’t be swayed by debate performances anyway.

Across the nation, election officials are reporting high demand for absentee ballots. Ballots already are available in a few states, and they will be ready in about 20 more this week. By the first week of October, absentee voting will have started in all but a handful of states. In most states, all registered voters will be eligible to vote absentee, and a growing number will take advantage.

By the middle of last week, South Carolina had collected 84 ballots from voters living overseas or in the military, said Chris Whitmire, spokesman for the state Election Commission. In Louisville, polling stations opened Thursday, with voting restricted to those who will be unable to show up on Election Day. In Virginia, Fairfax County started accepting absentee ballots Friday.

Early pressure

None of the early votes will be counted until Election Day, and in some states it could take days or weeks to count all absentee ballots. But in most states, the campaigns will be able to determine well ahead of Nov. 4 who’s voted early. Want the campaigns to stop bombarding you with fliers and phone calls? Vote early.

“That’s one less person we need to put a get-out-the-vote call to and one less person we need to send a mailer to,” said Nathan Treloar, communications director for the Iowa Republican Party.

Both presidential campaigns are pressing their supporters to vote early, trying to gain an advantage in a tight race. In past elections, the GOP has had a formidable “72-hour” program for getting voters to the polls in the final run-up to Election Day.

“What we have now is the 720-hour program,” said Rich Beeson, political director for the Republican National Committee, which is coordinating get-out-the-vote efforts for John McCain’s campaign. “It’s a two-week program, and in some cases, it’s a month.”

Obama’s campaign is targeting potential early voters state by state.

“We do everything we can to make sure our supporters know all the options available to them,” said Jon Carson, Obama’s national field director. “We’ve been building a massive ground game for all of this.”