After weeks of early and mail voting, at least 66 million Americans have already cast their ballots for next week’s election, a historic figure that has upended expectations about Election Day and which states could decide the presidential contest.

The massive number, which includes voters who have cast ballots either in person or by mail, has stunned election officials and campaign operatives. It equals close to half of the total turnout in 2016 – all but ensuring, with early voting continuing through the weekend, that the majority of ballots will be cast before Election Day for the first time in history.

The overwhelming demand to vote now – which has led to long lines nationwide – reflects a widespread sense of urgency to chart the country’s course over the next four years, despite the voting challenges posed by the coronavirus pandemic. And it puts this year’s election on pace for a rate of participation not seen since the early 1900s.

For now, the early numbers overwhelmingly favor Democrats in 16 of 19 states that provide such data. But the gap between Democratic and Republican voters has narrowed in recent days in several battleground states, and the campaigns of President Trump and former vice president Joe Biden noted that more Republicans are expected to vote on Nov. 3, Election Day, than Democrats, according to numerous polls.

Voters in Virginia wait in a long line to cast their ballots for the presidential election on Sept. 18, first day of early voting in that state. John McDonnell/The Washington Post

The question is how many more.

“The early vote is showing two things: We’re clearly headed to record-level turnout, nationally and likely in just about every state,” said Tom Bonier, the head of TargetSmart, a Democratic data firm. “And it’s clearly showing us that Democrats are highly engaged and will be themselves setting record levels of turnout.”

Bonier emphasized that Republicans are also motivated to vote. “The open question,” he said, “is whether that level of Republican engagement and enthusiasm can match or exceed (that of) Democrats. That’s the part of the equation that we can’t solve until Election Day.”

On Monday, Trump campaign manager Bill Stepien told reporters that the president will win the Election Day vote easily, in part because of an extensive get-out-the-vote operation. A person close to the Biden campaign, who spoke on the condition of anonymity to describe internal thinking, said it’s “absolutely possible” for Trump to catch up on Election Day.

The dynamic creates a significantly unsettled landscape as turnout has surged across the country – in cities and rural America, in battlegrounds long expected to decide who the next president will be, and in unexpected places that have not had competitive races in years. It also means that Election Day will feel substantially different from those in past years, with a smaller, more Republican turnout.

As of Monday night, the number of ballots cast had exceeded 60% of the 2016 vote in at least 14 states, including Florida, Georgia, Nevada, New Mexico, North Carolina, Tennessee, Vermont and Washington, according to state data and the U.S. Elections Project, which tracks early voting.

The project, run by Michael McDonald, a political scientist at the University of Florida, tallied 66.2 million ballots cast as of Tuesday morning, including 22 million in-person early votes.

Nowhere has the spike been more unexpected than in Texas, where more than 7.8 million voters had cast ballots as of Tuesday morning – more than 86% of the overall vote in 2016 – and where nine counties have surpassed their 2016 totals. Among them: deeply conservative Denton, northwest of Dallas; fast-growing Williamson, outside of Austin; and McCulloch, population 8,000, at the center of the state.

Both parties said excitement is evident in Republican strongholds as well as Democratic ones, making it difficult to glean an advantage for Trump or Biden. A Washington Post average of October polls shows the two candidates about even in the state; Trump won Texas by nine points in 2016.

“Even though you have people moving here and young people being more progressive, it’s still Texas,” said Crystal Flores, 22, a graduate student in San Antonio who said she relates to some of her relatives’ more conservative positions but voted early for Biden this month. “We grew up on conservative values.”

Fewer than 9 million Texans voted in 2016, out of 19 million voting-age adults at the time – a low turnout rate that Democrats said reflected the apathy of many of their own supporters.

The surge this year, meanwhile, comes amid a fight over many of the state’s down-ballot races. In the wake of Democratic former congressman Beto O’Rourke’s narrow loss to Republican Sen. Ted Cruz two years ago, a rush of candidates have mounted campaigns in Republican-held districts that had rarely been challenged. Cash has poured into those races, including legislative seats that could flip control of the Texas House.

Voters cast their ballots at the Meadows Mall Clark County polling station in Las Vegas on Oct. 21. Melina Mara/The Washington Post

Such enthusiasm is driving a potential reverse-coattails effect in other states as well, where Democratic challengers for U.S. Senate seats are outperforming Biden in many polls. In Georgia – where nearly 3 million voters had cast ballots as of Monday evening, 71% of the 2016 total – Democrats are within range of forcing runoffs in contests for two Republican-held U.S. Senate seats, according to the October polling average.

And some Republicans said privately that they fear they are at risk of losing control of the Georgia House, which, like legislatures nationwide, will draw new congressional district boundaries next year. The presidential race, meanwhile, is about even in The Post average.

The profiles of voters who have cast ballots early indicate that this year’s electorate could look very different from four years ago.

Black voters have turned out in large numbers in key states such as Georgia and North Carolina, citing the need to cast ballots at the first possible opportunity.

New voters have also turned out at a remarkable rate: As of Monday, voters who did not participate in 2016 accounted for 25.6% of early ballots cast nationally, according to a TargetSmart analysis.

And signs have emerged that young voters are on track to sustain the record turnout they displayed in the 2018 election.

A poll of 18- to 29-year-olds released Monday by the Institute of Politics at Harvard’s Kennedy School found that 63% of respondents said they would definitely be voting in the election, the highest such measure in the 20 years that the poll has been conducted. The finding was far higher than in 2016, when the same survey found that 47% of respondents said they would definitely vote.

The poll found that likely voters in the age group favored Biden over Trump 63% to 25%.

Josefine Jaynes, a 19-year-old challenging a Republican incumbent for a state assembly seat in western Wisconsin, said she used her social media accounts two weeks ago to encourage about 300 friends – and friends of friends and acquaintances – all younger than 30 to make a plan to vote.

She said that more than half responded quickly that they had in fact already cast ballots. Most, she said, were first-time voters. Some came home from college on weekends to vote early because they were worried about trusting their ballots to the Postal Service.

“It was really shocking,” she said. “I know these people. Some of them are not interested in politics.”

Likewise, unaffiliated voters have turned out in enormous numbers, said Glen Bolger, a Republican pollster, who said those voters are more likely to decide the presidential outcome than the turnout differential between registered Republicans and Democrats.

“Voters are fired up on both sides,” said Bolger, whose clients include Sen. Thom Tillis, R-N.C. “Yes, I’d rather see more Republicans voting early, but they’ve been dissuaded from doing that. But there’s no indication they’re not enthusiastic.”

He said he expects overall turnout – the proportion of eligible voters who actually cast ballots – to exceed all presidential elections since 1908.

The early-voting data from Florida and North Carolina, two states that by most measures Trump must win, reveal an advantage for Biden. The Post’s polling average shows the candidates about even in Florida and Biden up by four points in North Carolina.

In Florida, where more than 6.4 million voters have cast ballots so far, Democratic voters hold about a 300,000-vote turnout lead over Republicans, a deficit that some Democratic strategists think will be hard for the GOP to overcome.

The story is similar in North Carolina, where Democrats account for 52% of 3.4 million ballots cast as of Tuesday morning, compared with 47% for Republicans – about a 315,000-vote advantage. Republicans would need more than 60% of the Election Day vote to catch up, said Morgan Jackson, a Democratic strategist in the state.

“If that holds over the next five days – even if it dips a little bit – that becomes a really steep hill on Election Day,” he said. “There are a lot of Democrats left to vote. There are a lot of African Americans left to vote.”

Additionally, Democrats can focus on turning out a vastly smaller universe of voters on Election Day. And they will have less to lose if the ongoing spike in coronavirus cases or bad weather causes voters to stay home.

“We’ve baked all those votes,” Jackson said.

There is a limit to what can be gleaned from the partisan breakdown of who has voted so far; a person’s party affiliation doesn’t guarantee a vote for that party’s nominee.

Still, some Republicans have been frank that the Democratic advantage among early voters is alarming, and they have increased efforts to encourage their own voters to cast ballots now.

In recent days, registered Republicans have begun closing the early-vote gap among the total ballots cast in Florida, Iowa, North Carolina and Pennsylvania, according to state data that show a partisan breakdown of the early vote.

One striking sign of this year’s surge of enthusiasm is that voters have cast ballots in particularly strong numbers in some states that are not considered major battlegrounds – a sign, perhaps, that surprising results may pop up in unpredictable places once all the votes have been counted.

In Montana, for instance, turnout already exceeds 75% of the total 2016 vote – a likely result of a competitive Senate race between Republican incumbent Steve Daines and Democratic former governor Steve Bullock. And in heavily Republican Tennessee – which Trump won by 26 points four years ago – turnout is equal to about 65% of the total 2016 vote.