Over the next 10 days, President Bush and Sen. John F. Kerry will spend millions of dollars on a blizzard of last-minute ads. The candidates will dash from state to state, trying to squeeze in one more rally, a few thousand more handshakes. But for a growing number of people, the effort will be wasted: They have already voted.

Voters are casting tens of thousands of ballots a day in most of the 30 states that allow residents to vote early in person or to vote absentee without an excuse, including in some of the battleground states where the presidential race hangs in the balance.

As of Friday afternoon, more than 1.3 million people had voted in eight of the swing states, records indicate. Both parties are making a huge effort to get their supporters to the polls early and are reading the tea leaves to decide what, if anything, the early turnout numbers show.

In New Mexico and Nevada, about a tenth of the electorate is already "in the bank," in campaign parlance. Republicans had cast close to the same number of early votes as Democrats in the Las Vegas area, where about 70 percent of Nevada's population resides, while Democrats were running strong in the Reno area, historically a Republican stronghold.

In Iowa, where Democrats have long had an advantage in early voting, more than 200,000 ballots had been cast as of the start of this week.

In Florida, a sampling of eight counties showed a consistent pattern of Democrats turning out to cast early ballots in greater proportion than their share of registered voters, while Republicans were going to the early voting sites at or below what their registration percentages would suggest.

In Seminole County, for example, Democrats make up 31.7 percent of the registered voters but 40 percent of the early voters. The same was true in Republican-leaning Brevard County, where Fred Galey, supervisor of elections, said that he had no specific figures but that "many more Democrats" are casting ballots than Republicans.

In Osceola County, a Democratic bastion, Democrats are turning out for early voting in higher percentages than their share of registered voters, while Republicans are below their registration levels. The same was true in Hillsborough, the highly populated county where Tampa is located.

Mindy Tucker Fletcher, a spokeswoman for the Florida Republican Party, was not too worried: "They're doing well in their areas of the state, and we're doing well in ours," she said.

Charlie Baker, the Democrats' national early-voting guru, was similarly restrained.

"Conventional wisdom says Republicans are most likely to vote absentee and Democrats are more likely to vote early, but a lot of that, I think, is ancient history," he said. "The reality is we'll all have a far better handle on this after the election."

Part of the reason for the uncertainty is that early voting is a relatively new phenomenon, with the number of states offering it nearly tripling in the past eight years. Campaigns have been forced to adjust to a new presidential campaign rhythm: In Iowa, for instance, "Election Day" lasts more than five weeks.

This year, election officials say they are seeing record early-voting turnout, in part because of the enormous interest in the close presidential election and in part because of the get-out-the-vote effort by parties. A National Annenberg Election Survey released this week found that nationwide, 5 percent of voters have already cast a ballot and more than a fifth plan to vote before Election Day.

In states where early voting has existed for a while, election officials are predicting even greater numbers. In New Mexico, for instance, Secretary of State Rebecca Vigil-Giron (D) believes that more than 50 percent of voters will cast their ballots before Nov. 2, a big increase over 2000.

Republicans are hoping to bank as many voters through absentee and early voting as possible before turning to an intense get-out-the-vote campaign in the 72 hours before Election Day. In Iowa, a GOP mailer urged voters to "Defend America's Freedom" by voting "today."

Democrats, whose supporters tend to be less reliable voters, are counting on early voting to help them turn out those who irregularly show up at the polls and who may be juggling busy schedules.

In Colorado, where tens of thousands of voters have already cast ballots, Democrats mailed supporters a flier that includes a map of locations in the Denver area that offer a chance to vote early.

In Las Vegas, unions plan to bus casino workers to an early-voting site just off the Strip that is open all night, and this week a truck drove through some of the Hispanic neighborhoods as a Spanish-speaking man with a bullhorn encouraged residents to vote early.

By Thursday, more than 86,000 residents had cast ballots, an increase of almost 30 percent over the number who had done so by this time in 2000. An additional 20,000 had mailed back absentee ballots.

Clark County Registrar Larry Lomax said he is hopeful that a big early vote in Las Vegas could ease the crush of Election Day, eliminating long lines and potentially staving off other problems. Officials in Florida have also ironed out kinks during early voting there.

"I'm hoping that in Florida and elsewhere, early voting will be a pressure valve that can relieve some of the pressure of Election Day and give election officials a chance to work out problems," said Elliott Mincberg, legal director for the liberal People for the American Way Foundation.

Research editor Lucy Shackelford and researcher Madonna Lebling contributed to this report.

Lawrence Lyman, 72, seals his ballot in Iowa, where early voting started in September.Colorado Democrats were sent a flier with a Denver area map of where to cast ballots before Nov. 2. Thousands have already voted.