Early voting options grow in popularity, reconfiguring campaigns and voting preparation

While polling sites around the country are gearing up for huge voter turnout on Election Day, data and experts predict that a majority of the votes that will decide this year's key races will be cast months before.

In fact, many of those votes could be cast in the next few weeks.

Analysts who have been studying early-voting trends say mail-in balloting and voting done at early opening polling sites will not only be a crucial indicator for this year's races, but also future voting methods adopted by the country.

Early in-person voting options are available for almost all registered voters in 47 states with some allowing voters to cast their ballot as early as September, according to the National Conference of State Legislatures, which tracks election laws across the country.

Michael McDonald, a professor of political science at the University of Florida who helps run the school's election lab, told ABC News that early voting exploded during the 2020 election and its effectiveness has reshaped the way the electorate and campaigns navigate the election.

"People find it easier to navigate and return the ballot at their convenience and it gives them more chances. They're more likely to cast a ballot with those options," he said.

How and where voters can cast a ballot early

In addition to offering voters a chance to cast their ballot through the mail, many states offer voters two ways of casting a ballot in person: either dropping off their absentee ballot at an election office or site, known as in-person absentee voting; or at a polling machine polling place that is open prior to Election Day.

As of 2024, 22 states offer all voters who vote via absentee the option to turn in their ballot in person early, according to NCSL data.

Alabama and New Hampshire offer no in-person early voting options -- something the state's election officials have not opted to do. Mississippi only offers in-person absentee to voters who meet specific criteria such as a physical disability, or proof that they will not be in the state on Election Day, such as military members.

Twenty-seven states and the District of Columbia give voters both in-person absentee and early in-person poll site options, NCSL data shows.

Eight states -- California, Oregon, Washington, Nevada, Utah, Colorado, Vermont and Hawaii -- and D.C. have adopted all-mail ballots and allow voters to cast their ballots in person before Election Day. With this process, states mail ballots to all registered voters and they can send it back, drop it off in-person absentee or ballot box, or simply choose to vote in a polling site either early or on Election Day.

Some election offices will offer voters a chance to submit their paper ballots in person as early as mid-September.

​In Pennsylvania, some voters may be able to apply for and then cast mail-in or absentee ballots in person at their county's election office starting around Sept. 16, which is the date for when counties must begin processing applications for mail-in or absentee ballots. The Pennsylvania Department of State told ABC News, however, that counties might not necessarily have the ballots ready by that date, due to pending litigation that could impact who appears on the ballot.

Rise in popularity

Charles Stewart, the director of Massachusetts Institute of Technology's election data science lab, told ABC News that voting data has shown a gradual increase in votes cast before Election Day over nearly three decades.

In fact, during the 2020 election, more than 69% of votes cast in the election were done through either mail-in ballots or early in-person voting, according to election data. By comparison, only 40% voted early in the 2016 election and 33% in the 2012 election, the data showed.

The data did not indicate how many mail ballots were turned in person.

Stewart noted that the pandemic was a factor behind the 2020 surge in early voting, and even though there was a decrease in early voting numbers during the 2022 midterms, there was still a jump in the number of people who cast their ballots either through the mail or at an early-voting site compared to previous midterms.

"If you extend the trend line and extend it to 2022, there is only a little bit more voting by mail," he said. "That tells me that voters have, on aggregate, returned to patterns we saw before 2020, which is that of a slowly growing reliance on convenience voting methods."

The extra convenience isn't the only incentive that is moving more voters to early voting, particularly mail-in ballots, according to Stewart.

Stewart said that several studies that have been published about voting behaviors have shown that voters who cast their ballot through the mail are thinking about their choices "more deeply and thoroughly."

"I heard it from a voter the other day who said they appreciate being able to lay the ballot on the table and do the research on the issues and the candidates," he said.

The enthusiasm has also had ripple effects, according to research conducted by McDonald.

McDonald said that data has shown that the states that opted to give all registered voters their ballot in the mail, such as Colorado, Washington and Oregon, saw the highest turnout rates in the country in 2020.

"In the early states that opted [into] mail balloting, places like Oregon and Washington, they've done satisfaction surveys and voters there love it, both Democrats and Republicans," he said.

A boon for voters, election offices and campaigns

Election experts said that 2020's jump in early voting helped to decrease long lines on Election Day at a time when the pandemic required smaller indoor crowds and social distancing.

Even though the need to decrease crowds has lessened, McDonald stressed there is still a need for "safety valves" when it comes to Election Day lines.

"It means if someone has a problem … and they try to catch their problem earlier, they have more time to rectify that problem," he said, citing examples such as an error on their form or improper voter ID.

McDonald also cited the sudden snowstorm that hit northern Arizona in November 2022 as a major obstacle that voters and election offices faced when it came to Election Day voting.

"These are the things that can happen and campaigns kind of know they shouldn't rely too much on Election Day because there could be things that go wrong," he said.

Christopher Mann, the research director for the non-profit group, The Center for Election Innovation & Research, told ABC News that early voting also gives election office teams, many of whom are understaffed and underfunded, extra time to handle the large number of ballots that come through during presidential cycles.

"They can move more people around during those early weeks, especially on the weekends," he said.

At the same time, early voting has reshaped how campaigns are conducted.

Former President Donald Trump and President Joe Biden pushed for their debates to take place prior to October because of early voting. Trump and Vice President Kamala Harris are scheduled to debate on Sept. 10 on ABC News.

Aside from the campaign trail, McDonald said that early voting also affects the campaign staffers on the ground who receive voter information from election offices.

"Then the campaigns can say, 'OK this voter already voted, I don't need to call them or mail them something. I can scratch them off the list," he said.

Trump's false claims on early voting shift dynamics

In both the 2020 election and in this year's contest, Trump has been vocal about his distrust in early voting, falsely claiming it is not secure and pushed for only voting on Election Day.

Despite appearing in a video at the Republican National Convention encouraging Republicans to vote by mail or early if available, Trump has been criticizing early voting at his events.

"We should have one-day voting. We should have paper ballots, we should have voter ID, and we should have proof of citizenship," he told reporters at a news conference last month.

McDonald said Trump's rhetoric led to a major shift in the 2020 election as the number of Republicans who voted by mail dropped compared to Democrats. Prior to 2020, more Republicans cast their vote in the mail, according to McDonald.

"We can see that those patterns really haven't restored themselves [to] pre-pandemic," he said.

The election experts stressed that there is no evidence of fraud when it comes to mail-in ballots and, in fact, showed there is no correlation between the number of early votes cast and the outcome of the election.

"If you look at states where half of the ballots were issued before Election Day, Trump won half of that vote," Mann said.

The experts say the election data is showing an upward trend of more voters opting to vote early versus on Election Day, with mail-in voting seeing the biggest increases, and they predict more states will expand those early voting offerings.

Stewart noted that the momentum is still there as several states failed to pass measures in the last four years that would have restricted early-voting options, specifically ending pandemic-era rules that allowed for no-excuse absentee.

Ultimately, Stewart contended that giving voters as many options to safely and properly cast their ballot leads not only to more convenience, but a stronger electorate.

"I would encourage voters to think about their own lives, their own habits, their own values and choose their mode that is keeping with all of those things," he said.

ABC News' Oren Oppenheim contributed to this report.

Editor's note: This story has been updated to clarify the types of early-voting ballots Pennsylvanians can apply for and that Sept. 16 is around the time those applications can begin.