The first mail ballots get sent to voters in less than two weeks and early in-person voting will start as soon as Sept. 20 in some states as election season kicks off.
The first batch of ballots typically sent out go to military and overseas voters. Under federal law, that must happen at least 45 days before an election — which this year is Sept. 21.
Some states start earlier. North Carolina will begin sending mail ballots to all voters who request them, including military personnel and overseas voters, in just two weeks, Sept. 6.
Voter registration deadlines vary by state, with most falling between eight and 30 days before the election, according to the National Conference of State Legislatures. The deadline is Oct. 7 in Georgia, one of this year's most prominent presidential battlegrounds.
Nearly all states offer some version of in-person voting, though the rules and dates vary considerably. In Pennsylvania, another of the major presidential battleground states, voters can visit their local election office to request, complete, and return a mail ballot beginning Sept. 16. For those counting, that's about three weeks from now.
Before the first ballots are even cast, both camps are gearing up to fight over voting.
Battles over election rules have become a staple of American democracy, but they're expected to reach new heights this year.
Trump installed his own leadership team at the Republican National Committee, including a director of election integrity. The RNC has filed a blizzard of lawsuits challenging voting rules and promises that more are on the way.
Democrats also are mobilizing and assembling a robust legal team. Among other things, they are objecting to GOP efforts to remove some inactive voters or noncitizens from voter rolls, arguing that legal voters will get swept up in the purges.
Information from The Associated Press was used in this report.