(Adds number of early votes passing 4 million)
By John Whitesides
WASHINGTON, Oct 8 (Reuters) - Americans are rushing to cast ballots ahead of the Nov. 3 election at an unprecedented pace, early voting numbers show, indicating a possible record turnout for the showdown between President Donald Trump and Democratic challenger Joe Biden.
With less than four weeks to go before Election Day, more than 6.6 million Americans already have voted, more than ten times the number who had at this time in 2016, according to the United States Elections Project, which compiles early voting data.
The shift has been driven by an expansion of early and mail-in voting in many states as a safe way to cast a ballot during the coronavirus pandemic and an eagerness to weigh in on the political future of Trump, said Michael McDonald of the University of Florida, who administers the project.
"We've never seen this many people voting so far ahead of an election," McDonald said in an interview earlier this week. "People cast their ballots when they make up their minds, and we know that many people made up their minds long ago and already have a judgment about Trump."
The early surge has led McDonald to predict a record turnout of about 150 million, representing 65% of eligible voters, the highest rate since 1908.
Biden leads Trump in national opinion polls, although surveys in crucial battleground states indicate a tighter race.
The numbers reported so far come from 34 states plus the District of Columbia. All but about a half-dozen states allow some level of early in-person voting.
The percentage of voters who cast their ballot at a voting machine on Election Day already had been in steady decline before this year, according to the U.S. Election Assistance Commission, a federal agency.
The total number of early or mail-in votes more than doubled from nearly 25 million in 2004 to 57 million in 2016, it said, representing an increase from one in five of all ballots cast to two in five of all ballots cast.
Trump has railed against mail-in voting, making unfounded accusations that it leads to fraud. Experts have said such fraud is rare.
Those attacks by the president have shown signs of depressing Republican interest in voting by mail. Democrats have more than doubled the number of returned mail-in ballots by Republicans in seven states that report voter registration data by party, according to the Elections Project.
A national Reuters/Ipsos poll taken last week found 5% of Democrats nationwide said they had already voted compared to 2% of Republicans. About 58% of Democrats planned to vote early compared to 40% of Republicans. https://tmsnrt.rs/30AJKMd
McDonald said early voting typically starts strong, then drops before surging just ahead of the election. But in some states, rates of participation already have skyrocketed a month out.
(Reporting by John Whitesides; Editing by Scott Malone and Aurora Ellis)
Our Standards: The Thomson Reuters Trust Principles.