Polling locations will be open from 6 a.m. to 7 p.m. local time and voters in Arizona must return their absentee mail-in ballots by 7 p.m.
Arizona is one of the top battlegrounds to watch in 2020. With shifting demographics, the state has become purple and is considered in play for Democrats.
It's also home to a highly competitive and expensive Senate race in which Sen. Martha McSally is defending her seat against Democratic challenger Mark Kelly.
In 2016, President Donald Trump won the state by just over three points. The vote will likely come down to Maricopa County, home to Phoenix and the state's largest voting bloc.
*Counties are colored red or blue when the % expected vote reporting reaches a set threshold. This threshold varies by state and is based on patterns of past vote reporting and expectations about how the vote will report this year.