While polling stations across the nation are preparing for high voter participation on Election Day, data and experts predict that a significant portion of votes determining the outcome of key races will be cast well in advance.

In actuality, a significant portion of these votes could be cast within the next few weeks.

Analysts specializing in early voting trends suggest that mail-in voting and participation at early opening polling locations will not only serve as a critical indicator for this year's races, but also influence future voting methods adopted across the nation.

Early in-person voting options are accessible to nearly all registered voters in 47 states, with some states permitting voting as early as September, according to the National Conference of State Legislatures, which monitors election laws nationwide.

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

"These options offer voters greater flexibility and convenience, making it easier for them to participate in the election process and potentially leading to higher turnout," he said.

How and where voters can cast a ballot early

In addition to mail-in voting, numerous states offer voters two ways to cast their ballot in person: by dropping off their absentee ballot at an election office or site, known as in-person absentee voting; or by voting at a polling place that is open before Election Day.

As of 2024, NCSL data indicates that 22 states provide all voters who opt for absentee voting the ability to submit their ballots in person before Election Day.

Alabama and New Hampshire do not offer any in-person early voting options -- something that state election officials have not chosen to implement. Mississippi only offers in-person absentee voting to voters who meet specific requirements such as a physical disability, or proof that they will be out of state on Election Day, like military members.

According to NCSL data, twenty-seven states and the District of Columbia offer voters the choice between casting their ballot in person at an early voting location or by mail.

Eight states -- California, Oregon, Washington, Nevada, Utah, Colorado, Vermont and Hawaii -- and the District of Columbia have adopted voting by mail as their primary system, allowing voters to cast their ballots either by mail or in person before Election Day. Under this system, states distribute ballots to all registered voters, who can then return them by mail, drop them off at an in-person location, or vote at a polling place on Election Day or during early voting.

Some election offices will provide voters with an opportunity to submit their paper ballots in person as early as mid-September.

​In Pennsylvania, some voters may be able to cast absentee ballots in person at their county's executive office starting 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
, however, that counties might not necessarily have the ballots ready by that date.

Rise in popularity

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

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

The data didn't specify how many mail ballots were submitted in person.

Stewart pointed out that the pandemic contributed to the surge in early voting in 2020. Even though early voting numbers decreased during the 2022 midterms, there was still a significant increase in the number of people who voted by mail or at early voting locations compared to previous midterms.

"If you project the current trend forward to 2022, there will only be a slight increase in voting by mail," he said. "This suggests that voters, as a whole, have returned to the patterns we observed before 2020, where there was a gradual increase in the use of convenient voting methods."

The increased ease of voting isn't the only factor driving more voters to early voting, especially mail-in ballots, according to Stewart.

Stewart mentioned that several research papers about voting habits have demonstrated that voters who cast their ballot by mail are thinking more carefully and thoroughly about their choices.

"I heard a voter say the other day that they appreciate being able to take their time with the ballot, looking up information about the issues and the candidates," he said.

The excitement has also spurred additional effects, according to a study by McDonald.

McDonald stated that research indicates that states which mailed ballots to all registered voters, like Colorado, Washington, and Oregon, witnessed the highest voter turnout rates nationwide in 2020.

"In the initial states that adopted mail-in balloting, such as Oregon and Washington, they have conducted satisfaction surveys, and voters there overwhelmingly favor the system, both Democrats and Republicans," he said.

A boon for voters, election offices and campaigns

Election experts noted that the surge in early voting in 2020 helped alleviate long lines on Election Day, particularly during the pandemic when smaller indoor gatherings and social distancing were necessary.

While the need to reduce crowds has decreased, McDonald emphasized the continued importance of having "safety nets" for potential long lines on Election Day.

"It means if someone encounters a problem … and they try to address it early on, they have more time to fix the issue," he explained, citing examples such as an error on their application or an incorrect voter ID.

McDonald also mentioned the unexpected snowfall that hit northern Arizona in November 2022 as a significant challenge faced by voters and election officials on Election Day.

"These are potential issues, and campaigns understand they shouldn't rely heavily on Election Day because unforeseen problems could arise," he said.

Christopher Mann, the research director for the non-profit group, The Center for Election Innovation & Research, told
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.

"Campaigns can deploy more resources during those initial weeks, particularly over the weekends," he stated.

Simultaneously, early voting has transformed the way 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
.

Beyond the campaign trail, McDonald noted that early voting also impacts campaign staff in the field who obtain voter information from election officials.

"Then campaigns can say, 'We know this voter has already cast their ballot, so we don't need to contact them further. We can remove them from our outreach lists,'" he explained.

Trump's false claims on early voting shift dynamics,

In both the 2020 election and the current contest, Trump has been outspoken about his mistrust of early voting, falsely claiming it is insecure and advocating for voting exclusively 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 rallies.

"We should have a single day for voting. We should use paper ballots, require voter identification, and demand proof of citizenship," he told reporters at a press conference last month.

McDonald attributed Trump's rhetoric to a substantial shift in the 2020 election, with a decrease in mail-in voting among Republicans compared to Democrats. Before 2020, more Republicans tended to vote by mail, according to McDonald.

"We observe that these patterns haven't reverted to their pre-pandemic levels," he noted.

Election experts emphasized that no evidence supports claims of fraud related to mail-in ballots. In fact, they presented findings demonstrating no relationship between the number of early votes and election outcomes.

"In states where a significant portion of ballots were cast before Election Day, Trump secured a considerable share of those votes," Mann stated.

Election data reveals a growing trend of voters choosing early voting options, particularly mail-in voting, over Election Day voting. Experts anticipate more states will expand these early voting choices.

Stewart pointed out that the push for expanded voting access continues, as several states have failed to pass measures in the past four years that would have curtailed early-voting options, particularly ending pandemic-era policies allowing for absentee voting without justification.

Ultimately, Stewart argued that providing voters with numerous options to cast their ballot safely and appropriately leads not only to greater convenience but also a more robust electorate.

"I urge voters to consider their personal lives, their own habits, their own principles and select a voting method that aligns with all of these factors," he stated.

' Oren Oppenheim contributed to this report.