MIAMI — In this must-win state for President Donald Trump, lines snaked for blocks Monday on the first day of early voting, longstanding traditions were upended, and Sen. Kamala Harris encouraged voters at a drive-in rally to blare horns.

Both campaigns watched nervously: Once again, Florida goes into the final weeks of a presidential campaign as an anxiety-driving toss-up.

Voters seemed as anxious as the campaigns. Some fretted that Joe Biden would import socialism, others worried Trump would fail to contain the COVID-19 pandemic, and still others predicted that violence would erupt in the streets if the election results are contested.

The state is critical for reasons both practical and psychological: Without its 29 electoral votes, Trump would have tremendous difficulty finding a path to victory. And because the state processes its mail-in and early ballots in advance and counts them quickly, Florida’s near-final results likely will be known on election night, long before slower states like Pennsylvania and Michigan.

As in other states so far this year, voting seems headed for potential records. Even before early voting began Monday in 50 of the state’s counties, more than 2.5 million Floridians had voted by mail, representing more than a quarter of the total votes cast four years ago.

Registered Democrats have cast nearly a half million more of those ballots than Republicans, according to figures compiled by Unite the Country, a pro-Biden super PAC, and Democratic data firm Hawkfish.

That doesn’t have Biden’s campaign at ease, however, despite a small lead in state polls. Republicans have vastly outpaced Democrats on new voter registrations in the state since March.

“We are not taking our foot off the gas, and I expect a surge to the finish,” Joe Gruters, chairman of the Republican Party of Florida, said in a statement.

Democrats, who are as anxious to avoid overconfidence as the Trump campaign is to eschew defeatism, cite a host of unknowns. The flood of mail ballots cast on their side, for example, could be offset by Trump voters who heeded the president’s advice not to vote by mail and are holding their fire until Election Day, said Steve Schale, who ran the Barack Obama campaign in Florida in 2008 and now heads Unite the Country.

“There’s a lot more we don’t know than we know,” Schale said. “This is uncharted territory for everybody.”

Everything is upside down, Schale said. Usually the GOP is extremely disciplined about returning mail ballots, and Democrats have a tougher time.

“Donald Trump basically decided to take a match and just torch 20 years of Republican work down here,” Schale said. “Voters who have voted by mail for 20 years now don’t have confidence because of Trump’s tweets.”

At polling stations, Monday arrived with rain across the state, but voters were out in force regardless.

Among them was Lilliam Cespedes, a 75-year-old who joined the line outside Miami’s Kendall Branch Library, where voters took cover under pink, green and black and white umbrellas, scouring their voter guides.

Cespedes said she was there to rectify a mistake she made in 2016, when she voted for Trump.

“He’s had four years,” said the Cuban refugee, who arrived in America when she was 12. “What did he do?”

She was registered Republican until last year, when she switched to independent.

“I know that all my Cuban people vote for Trump, because Biden supposedly is a communist,” she said. “I’m willing to take a chance. How can a president say he’s not going to leave if he doesn’t win. That’s democracy? … I can’t put up with that. That’s what I lived.”

She is among the many older voters dismayed by Trump’s management of the pandemic, which she said “is absolutely killing people.”

There was no shortage of Trump supporters in line with Cespedes. Some wore their candidate preference proudly, decked out in Trump 2020 face masks or hats. Others were hesitant to share, citing potential backlash.

“We are very much afraid of people going against us,” said a Chilean woman, who declined to give her name before whispering that she would be voting for Trump. “You can see the other side is doing whatever they want. We put a flag in the house, they break our windows.

“It’s getting ugly. It’s getting very ugly,” she said from behind a white surgical mask.

Both campaigns are focusing heavily on the state’s Latino voters. While Trump has made major inroads with Cuban Americans, Biden is popular with Puerto Rican voters, and the campaign is making a big push for support from Colombian Americans.

Soon after the Kendall voting station opened, a brightly painted red, yellow and blue Chiva bus pulled up, of a type widely used in Colombia, and “cumbiamberas” disembarked to dance as men played tamboras, two-headed drums.

“I see lines. This is incredible,” said Rep. Debbie Mucarsel-Powell, D-Fla., who was part of the Biden campaign caravan.

Sixteen miles north, at the John F. Kennedy Library in Hialeah, the word “communism” rippled through the line, with many voters citing countries that Floridians had fled.

“We came from communism,” said Paula More, a Cuban immigrant who visited the polls with her husband and 30-year-old son to vote against Democrats. She warned the party is heading down that path “little by little.”

Across the street from the voting line, a crowd waved Trump flags and carried signs that read “no socialista no comunista somos capitalista.”

It’s a theme the Trump campaign has deployed extensively here as it tries to hold the votes of traditionally Republican Cubans and newer anti-communist immigrants from Venezuela and elsewhere in Latin America, warning Democrats will not take a hard line on Cuba and its allies.

Farther north, in Orlando, in the swing territory of central Florida, Martha Collins waited in line at the polling station at Alafaya Branch Library more than 3 1/2 hours before casting her ballot for Trump.

Kenneth Woodson, a retired police officer from New York, was no less determined to cast his ballot for Biden.

“I want him out of office because he has no interest in America,” the longtime Democrat said. Under Trump, “America’s a joke. We gotta get it back.”

Orlando was where Harris traveled for a pandemic-style drive-in rally, where she used a bit of Spanish to color her remarks.

“Loco,” she said, invoking the Spanish word for “crazy” to described Trump’s “weird obsession with trying to get rid of everything Barack Obama and Joe Biden created.”

The Biden campaign also sees potential for gains beyond the state’s large Latino populations. It is targeting white voters who sided heavily with Trump in 2016, hoping to win back some ground in places like the state’s conservative Panhandle. Polls have shown Biden picking up support in such areas.

By mid-afternoon, Harris was on a plane on her way to a rally in Jacksonville on the state northeastern coast, which has one of the state’s largest Black populations.

Biden has several potential paths to reelection, but his strategists know that a Florida win for him could mean a quick resounding victory for Democrats, rather than a long, excruciating vote count nationwide that extends for days or weeks.

“If Democrats win Florida,” said the Rev. Randolph Bracy, a retired pastor who introduced Harris in Orlando, “it’s game over.”