Nearly 100 million voters have already cast their ballots, leading to questions about how the record early turnout will impact results up and down the ballot. 

The unprecedented early vote has given Democrats hope going into Tuesday. Overall, Democrats have outperformed Republicans in early voting, after President Trump spent months waging baseless attacks on mail-in ballots.

Republicans for their part are hoping for a large in-person turnout on Election Day, though several swing states are seeing spikes in coronavirus cases, which could impact turnout. 

“I think it’s safe to say at this point that Joe Biden is headed into Election Day with a pretty substantial lead ... in battleground states,” said Tom Bonier, CEO at TargetSmart, a Democratic data firm. “It just becomes a question at this point of whether President Trump and his campaign can climb out of that hole.”

Then there's the issue of counting and reporting the results. In states where elections officials are allowed to start counting mail-in ballots before Election Day, experts say the early vote could smooth the process.

In others, however, officials aren't allowed to start to start counting mail-in ballots — this year a record number of them, including some that may not be received until after Election Day — until the morning of Nov. 3, meaning early results could appear to favor the president until the mail-in vote is tallied.

Trump on Sunday denied a report from Axios that he plans to declare victory if he has an early lead on Tuesday evening. But the president also signaled that Republican lawyers are gearing up to mount legal challenges to stop ballots from being counted if they are postmarked by Election Day but received days later in states such as Pennsylvania where Democrats have secured court victories.  

On Monday, Biden campaign manager Jen O’Malley Dillon threw cold water on the suggestion Trump could declare victory on election night, arguing it would be mathematically impossible. 

“Under no scenario will Donald Trump be declared a victor on election night, and that’s fundamentally how we want to approach tomorrow,” O’Malley Dillon said. 

While Democrats maintain a mail-in voting advantage, Republicans have caught up in some key swing states as in-person early voting has expanded. 

Nearly 9 million votes had already been cast in Florida as of Monday morning, which is 136 percent higher than the early turnout in 2016 and 95 percent of all the votes cast in 2016, according to the political tech firm Hawkfish, which was founded by Michael Bloomberg. 

Roughly two-thirds of Republican and Democratic voters have already voted in the state, with Democrats holding a lead of roughly 100,000 votes over Republicans. However, the gap between the two parties has narrowed significantly in the state, raising alarm bells for Democrats. 

Over a million Democrats cast mail-in ballots in the state two weeks ago, prior to the start of early voting, when Democrats led Republicans by 462,000 ballots. 

Democrats say the latest data doesn’t come as a surprise. 

"If you had said to me back in September, 'You’re going to go into Election Day 100,000 voters ahead with 150,000 more high-propensity Republicans left to vote,' I would have probably said, 'Let’s do it. Let’s take our chances with that,'" veteran Florida Democratic strategist Steve Schale said on a call with reporters for Hawkfish. 

Schale said that he was feeling good about particular parts of the state, including the I-4 corridor that stretches from Daytona Beach to Tampa. Schale added that Republicans typically have a turnout advantage in Miami-Dade County, the state’s most populous county. However, Schale said that does not mean he feels pessimistic about the whole of South Florida, noting that Democrats had high turnout in Broward and Palm Beach counties so far. 

“That doesn’t mean that I’m going to put a hundred dollars on an outcome,” he said. 

Republicans, meanwhile, say they are feeling confident that Trump will be able to hold Florida, which he won narrowly in 2016, pointing to reports of lagging Democratic voter turnout among Latinos in Miami-Dade County.

“That is a good sign for us. Obviously we can’t tell where the unaffiliated, no-party voters are going,” said Ford O’Connell, a GOP strategist based in Florida. 

However, the Biden campaign said that while the Sunshine State is important, the campaign does not necessarily need it to get the 270 electoral votes needed to win the presidency. 

“Donald Trump has a very narrow path to win,” O’Malley Dillon said. “He needs to win Florida. It is key to his path to victory, and we really can win to get to 270 without Florida, which is a significant advantage. We’re going to fight, and we’re going to go get Florida, but we don’t need it to get to 270.”

The University of Virginia’s election forecaster, Sabato’s Crystal Ball, rates Florida a toss-up that leans Republican in its Electoral College rating. 

Republicans are more worried about Arizona, where, for the first time in history, Democrats outperformed Republicans in early voting, indicating unprecedented enthusiasm among Democrats and putting added pressure on Republicans as Election Day draws nearer. 

Republicans had closed the gap on Friday and, as of Monday, both parties were essentially deadlocked in the early vote tally. Chuck Coughlin, a GOP strategist based in Phoenix, noted in an interview last week that Trump won Arizona in 2016 by less than 4 percentage points and Republicans had a 7 percentage point turnout advantage overall, meaning that the GOP turnout on Election Day in Arizona would need to be substantial for Trump to defeat Biden. 

Polling also shows an increase in turnout over 2016 among younger voters, those 18 to 29 years old, a demographic that typically favors Democrats. Younger voters are helping to drive a surge turnout in battlegrounds such as Michigan and even Texas and Georgia, the latter two being red states that Democrats had hoped to flip this election cycle. 

“Voting is a form of protest and the way that young people have engaged in early voting, to me, is a continuation of their engagement in the summer’s protest against racial unrest,” said Democratic strategist Basil Smikle. He said the strength of the youth vote hearkened back to former President Obama’s 2008 win. 

Some key battleground states, including Michigan and Pennsylvania, do not begin counting ballots until the day of the election, meaning that it could take much longer for those states to tally final results. Pennsylvania’s secretary of state said Sunday that it could be a matter of days until all ballots are counted. 

Others, including Florida and Arizona, have state laws that allow them to begin counting ballots weeks beforehand, meaning the results there may come in earlier and potentially give more clarity on the trajectory of the race. 

“In Arizona, a state that’s majority vote-by-mail, where we’ve seen nearly 80 percent of ballots cast already, Trump would need to get 60 percent of the remaining votes to win,” O’Malley Dillon told reporters on Monday. “That includes vote-by-mail ballots in Maricopa County that haven’t been counted yet and we believe will significantly break for us.”