DES MOINES, Iowa (AP) — Iowa voters are expected to cast ballots in record numbers for an election that will determine competitive races for president, U.S. Senate, U.S. House and state Legislature.

Nearly a million people have returned absentee ballots, and it's likely that more than half of the votes cast will have come before Election Day. Polls will open Tuesday at 7 a.m. and voting will continue until 9 p.m.

CONGRESS

U.S. Sen. Joni Ernst breezed to an easy win in 2014 but has been in a much tighter race this year against Democrat Theresa Greenfield, who heads a Des Moines property development company. The race has been among the most expensive in the nation, reflecting on its importance in determining if Republicans maintain their Senate majority.

The races for three of the state's four U.S. House seats also could be close, and even the final race in a conservative district in western and northern Iowa likely will be more competitive than usual.

In the 1st District, freshman Democrat Abby Finkenauer is defending her seat against Republican challenger Ashley Hinson, a state legislator and former television news anchor.

In the 2nd District, Democrat Rita Hart and Republican Mariannette Miller-Meeks are running for a seat left open by the retirement of Democrat Dave Loebsack. It's the fourth time Miller-Meeks has run for the seat. She lost to Loebsack in 2008, 2010 and 2014.

Democratic Rep. Cindy Axne is running to retain her seat in the 3rd District against Republican David Young, who lost to Axne in 2018 after two House terms.

Polls have shown a competitive race in the conservative 4th District between Republican state Sen. Randy Feenstra and Democrat J.D. Scholten. Feenstra received the Republican nomination over U.S. Rep. Steve King, who beat Scholten by only 3 points in the 2018 election.

PRESIDENT

President Donald Trump won Iowa by more than 9 points in 2016 but polls have shown a much tighter race this year. Both candidates held events in Iowa in the days leading up to Tuesday's election.

LEGISLATURE

Democrats are optimistic about their chances of winning a majority in the state House and breaking four years of Republican control of both chambers as well as the governor's office. To do so, they will need to flip four seats, and Democrats contend they have multiple opportunities. Republicans now have a 53-to-47 seat edge in the chamber.

Democrats could make gains in the state Senate, especially in a year when seven Republicans have opted not to seek reelection. However, Republicans are expected to retain control given they now have a 32-18 seat advantage.

EARLY VOTES

Early voting has been gaining in popularity for years, and the movement was turbocharged this year by concerns about voting at polling places at a time when coronavirus cases continue to increase. Early voters broke earlier records a week before Election Day, with 64% of active Democratic voters and 42% of Republicans requesting an absentee ballot. In total, more than 950,000 ballots had been returned to election offices by Monday in a state with just over 2 million registered voters.

Although Democrats cast far more early votes, Republicans were expected to turn out strongly on Election Day. Many independent voters also will likely cast ballots in person since fewer than a quarter of them requested absentee ballots.

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Find AP’s full election coverage at APNews.com/Election2020.