Two U.S. Senate races were still uncalled on Monday, Nov. 9, with Democrats holding razor-thin leads over Republican incumbents in Alaska and Mississippi.

Why it matters: Democrats have already won control of the Senate with 54 seats to Republicans' 44, so the two races will decide how big their majority is, USA Today reported.

Mississippi

Democrat Scott Colom led Sen. Cindy Hyde-Smith 49.1% to 48.8%, or 467,930 votes to 465,356, with about 97% of the expected vote counted, according to Associated Press results. A win would make Colom the state's first Black senator since Reconstruction.

Absentee ballots count if received by Tuesday, and voters with ID issues on affidavit ballots have until Tuesday to fix them. Counties must certify results by Friday. Mississippi law has no provision for a statewide recount, the AP said. "We are not backing down," Hyde-Smith said. "This election is not over."

Alaska

Democrat Mary Peltola led Sen. Dan Sullivan 48.2% to 47.9%, or 102,962 votes to 102,325, in the AP's count. About three-quarters of the vote had been counted. Alaska uses ranked-choice voting, and that tabulation cannot start until Nov. 18, USA Today said.

Related: Congress returns for its lame-duck session.