Midterm elections live updates: Voters heading to polls today for high-stakes midterms

On election eve, in the race for the wide-open U.S. Senate seat in Iowa, Republican Rep. Ashley Hinson told the press that President Donald Trump's visit in Dubuque helped her get her final message out to voters.

"Josh Turek's too liberal for Iowa, and I think the president helped tell that story," she said. She again attacked her opponent on transgender issues and immigration, despite Turek saying he opposes men playing in women's sports and is willing to work with the president to secure the border.

Pressed on whether she had put enough distance between herself and the president, Hinson said that she delivered for Iowans under President Joe Biden and when Nancy Pelosi was speaker of the House.

"I'm always going to be somebody's ally if they're willing to work with me on something that's right for Iowa, but I will be a thorn in their side if they are wrong for Iowa," she said.

When asked about the integrity of the election, Hinson pledged to accept the outcome.

"It's easy to vote and hard to cheat here in Iowa. I'm confident that I will win, and I will accept whatever the outcome is tomorrow, but I believe that outcome will be that I'm going to be the next United States senator," she said.

-ABC News' Gaby Vinick

After months of candidates campaigning, Tuesday marks the midterm elections.

The balance of power in both the U.S. Senate and the U.S. House of Representatives is up for grabs on Tuesday as Republicans and Democrats vie for seats in key races across the country. There are also significant races for governor around the country.

More than 57 million early votes have been cast nationwide as of Monday afternoon, according to the Election Lab at the University of Florida. That number is set to outpace the more than 58 million total number of early votes cast in 2022.

-ABC News' Oren Oppenheim

An analysis of Federal Election Commission data by campaign finance tracker, OpenSecrets projects that spending on the 2025-2026 election cycle will reach about $12 billion -- meaning that, at the federal level, this cycle is slated to be the most expensive midterm election on record.

An analysis by AdImpact that incorporated gubernatorial elections found it to be the most expensive cycle on record, surpassing even the 2023-2024 general election cycle.

Advertising spending across House, Senate and gubernatorial races this cycle cost about $7.1 billion, according to an analysis by the Wesleyan Media Project. About $1.4 billion of that ad spending occurred late in the cycle, between Oct. 12 and Oct. 25.

-ABC News' Will Lennon