Candidates of all political stripes are latching on to the tantalizing reality that a huge - and growing - chunk of voters will cast ballots well ahead of Election Day.
They know the pot of votes is big. They know it requires different campaign strategies. They just can't agree on how to capture it.
Some are spending more money earlier. Others are trying to gradually dole out their stash of cash. Some are courting loyal supporters first. Others are trying to lock in unreliable voters. Some are rushing out ads. Others are pumping up early phone contacts.
Whatever the strategy, more and more candidates are keenly aware their campaigns must have a smart early-vote program.
"If they don't, the manager should be sued for malpractice," said Dave Boomer, campaign manager for Rep. Lee Terry, a Nebraska Republican in a competitive race this fall.
More people, too, are figuring out that early voting has benefits for them beyond the convenience of voting at the time of their own choosing. It's dawning on people that once they cast their ballots, those annoying phone calls and mailings from politicians and their allies might slow down or even stop.
With each election, early voters make up a bigger share of the American electorate.
In 2008, about 30 percent of all votes - one in three - came in ahead of the election, either by mail or in person. If the numbers are similar this year, as expected, that would be a substantial jump from the 20 percent who voted early in the last midterm elections, in 2006. In 1992, by contrast, just 7 percent of ballots - one in 14 - came in early.
The trend away from voting on Election Day gained momentum after the contentious 2000 presidential election, which inspired a wave of election overhauls. At least 33 states now offer some sort of no-excuse-needed early voting.
In some states, such as Colorado, the early-voting habit is so ingrained that it's "part of the fabric of the campaign," said Floyd Ciruli, an independent pollster in Denver.
In other states, such as Maryland, early voting is still so new that the candidates for governor have squabbled over its merits. Republican challenger Robert L. Ehrlich Jr., who vetoed an early-voting law when he was governor, called it "a solution in search of a problem."
Dan Tokaji, an early-voting expert and professor at Ohio State University's Moritz College of Law, said evidence is mixed on whether early voting increases turnout.
"It's not likely to result in a seismic shift in turnout, but it can make a difference in close races," he said. "There may be some voters teetering on the edge in terms of whether they'll come out to vote."
Overall, in a year that's looking grim for Democrats, Mr. Ciruli says, "if anything can save them, or at least diminish the losses," it's going to be an even more sophisticated early-vote operation than the party ran in 2008, when Barack Obama's campaign did a masterful job of banking ballots ahead of Election Day.
This year's primary elections offer ample evidence of the perils of ceding the early vote.
In Texas, GOP strategist Corbin Casteel said he saw a number of state House races in which candidates spent money late and did well with Election Day voters, but were dragged down by the early-vote results.
"If they had a stronger get-out-the-vote effort during early vote, they could have won," Mr. Casteel said. "It's extraordinarily important."
In Tennessee, state Senate Speaker Ron Ramsey, who came in third in a spirited primary for the Republican gubernatorial nomination, lamented that he didn't have enough money to get his message out at the kickoff of early voting because he had to make his cash last.
"I would have loved to have an extra $1 million in the bank, and peaked a week before that," he said.
Early-vote strategies vary wildly.
In Colorado, where early voters were instrumental in Democratic Sen. Michael Bennet's winning campaign against a strong primary challenger, Mr. Bennet worked hard to bank the early ballots of unlikely voters - those who had never voted in a primary or had done so just once. Sixty-six percent of his early ballots came from this group, according to the campaign.
In Ohio, Republican strategist Mark Weaver said early voting means campaigns have to reach out to voters much sooner, and that means candidates must either "raise more money or spread the peanut butter on the bread a little further."