Following Tuesday's vote, U.S. Sen. Gary Peters, a Democrat, was trailing GOP businessman John James in the critical swing state of Michigan.

James held a double-digit lead for much of the night until Peters started closing the gap early Wednesday, reports said. The race, still considered too close to call, could decide whether Republicans keep control of the Senate -- or Democrats win the majority.

“It’s pretty clear we’re not going to know the results until sometime tomorrow,” Peters said at an event in Pontiac, Mich., on Tuesday night, according to Grand Rapids' WOOD-TV. “A number of jurisdictions are still processing this massive amount of absentee ballots. … Stay tuned.”

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Sen. Gary Peters, D-Mich., speaks at a campaign event before Democratic vice presidential candidate Sen. Kamala Harris, D-Calif., Tuesday, Tuesday, Nov. 3, 2020, in Southfield, Mich. (Associated Press)

With roughly 80% of the votes counted as of 5 a.m., Peters trailed James by roughly 6 percentage points, Fox News election data showed.

“There’s still a lot of votes to be counted to be sure. But we’re extremely excited and optimistic about where we stand right now," James told supporters in Detroit, according to WOOD.

With control of the Senate on the line, money poured into the race. The Peters-James face-off was expected to top $100 million in spending, making it the most expensive election in Michigan's history, according to the Michigan Campaign Finance Network.

James, an Iraq War veteran, would be the first African American elected to represent Michigan in the Senate. If successful, he'd join Sen. Tim Scott of South Carolina as one of two current GOP Black senators.

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Republican U.S. Senate candidate John James speaks after dropping off his ballot in Farmington Hills, Mich., in this Oct. 26, 2020 file photo. (Associated Press)

Michigan hasn't elected a Republican to the Senate since 1994.

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“This Senate race isn’t about me, it’s about the people of Michigan," James said last month. "I’m not waiting until I’m in office to make a difference in my community, I’m doing it now. I’m far from perfect, but I do my best to put Jesus’ teachings of love into action by loving my neighbor as myself."

Fox News' Marisa Schultz contributed to this report