With eight days before Election Day, more people already have cast ballots in this year's presidential election than voted early or absentee in the 2016 race as the start of in-person early voting in big states led to a surge in turnout in recent days.

The opening of early voting locations in Florida, Texas and elsewhere has piled millions of new votes on top of the mail ballots arriving at election offices as voters try to avoid crowded places on Nov. 3 during the coronavirus pandemic.

The result is a total of 58.6 million ballots cast so far, more than the 58 million that The Associated Press logged as being cast through the mail or at in-person early voting sites in 2016.

Democrats have continued to dominate the initial balloting, but Republicans are narrowing the gap. GOP voters have begun to show up at early in-person voting, a sign that many heeded President Donald Trump's unfounded warnings about mail-voting fraud.

On Oct. 15, Democrats registrants cast 51% of all ballots reported, compared with 25% from Republicans. On Sunday, Democrats had a slightly smaller lead, 51% to 31%.

The early vote totals, reported by state and local election officials and tracked by the AP, are an imperfect indicator of which party may be leading. The data only shows party registration, not which candidate voters support. Most GOP voters are expected to vote on Election Day.

Analysts said the still sizable Democratic turnout puts extra pressure on the Republican Party to push its voters out in the final week and on Nov. 3. That's especially clear in closely contested states such as Florida, Nevada and North Carolina.

"This is a glass half-full, glass half-empty situation," said John Couvillon, a Republican pollster who tracks early voting closely. "They're showing up more," he added, but "Republicans need to rapidly narrow that gap."

In Florida, for example, Democrats have outvoted Republicans by a 596,000 margin by mail, while Republicans only have a 230,000 edge in person. In Nevada, where Democrats usually dominate in-person early voting but the state decided to send a mail ballot to every voter this year, the GOP has a 42,600 voter edge in-person while Democrats have an 97,500 advantage in mail ballots.

"At some point, Republicans have to vote," said Michael McDonald, a University of Florida political scientist who tracks early voting on ElectProject.org. "You can't force everyone through a vote centre on Election Day. Are you going to expect all those Republicans to stand in line for eight hours?"

Campaigns typically push their voters to cast ballots early so they can focus scarce resources chasing more marginal voters as the days tick down to Election Day. That usually saves them money on mailers and digital ads -- something the cash-strapped Trump campaign would likely want -- and minimizes the impact of late surprises that could change the race.

Trump's campaign has been pushing its voters to cast ballots early, but with limited success, delighting Democrats. "We see the Trump campaign, the RNC (Republican National Committee) and their state parties urging Trump's supporters to vote by mail while the president's Twitter account says it's a fraud," Tom Bonier, a Democratic data analyst, said on a recent call with reporters. "The Twitter account is going to win every time."

But Bonier warned that he does not expect a one-sided election. "There are signs of Republicans being engaged," he said. "We do expect them to come out in very high numbers on Election Day."

That split in voting behaviour -- Democrats voting early, Republicans on Election Day -- has led some Democrats to worry about Trump declaring victory because early votes are counted last in Rust Belt battlegrounds. But they're counted swiftly in swing states such as Arizona, Florida and North Carolina, which may balance out which party seems ahead on election night.

Some of the record-setting turnout has led to long lines at early-vote locations, and there have been occasional examples of voters receiving mail ballots that are incorrectly formatted. But on a whole, voting has gone relatively smoothly. With more than one-third of the 150 million ballots that experts predict will be cast in the election, there have been no armed confrontations at polling places or massive disenfranchisement that have worried election experts for months.

One sign of enthusiasm is the large number of new or infrequent voters who have already voted -- 25% of the total cast, according to an AP analysis of data from the political data firm L2. Those voters are younger than a typical voter and less likely to be white. So far similar shares of them are registering Democratic and Republican.

They have helped contribute to enormous turnouts in states such as Georgia, where 26.3% of the people who've voted are new or infrequent voters, and Texas, which is expected to set turnout record and where 30.5% are new or infrequent voters.

The strong share of new and infrequent voters in the early vote is part of what leads analysts to predict more than 150 million total votes will be cast and possibly the highest turnout in a U.S. presidential election since 1908.

"There's a huge chunk of voters who didn't cast ballots in 2016," Bonier said. "They're the best sign of intensity at this point."