U.S. Sen. Jon Tester, D-Mont., speaks while standing next to his wife, Sharla, at a campaign rally, Thursday, Sept. 5, 2024, in Bozeman, Mont. (AP Photo/Matthew Brown)

U.S. Sen. Jon Tester, D-Mont., speaks about reproductive freedom at a campaign rally with his supporters, Thursday, Sept. 5, 2024, in Bozeman, Mont. (AP Photo/Matthew Brown)

FILE - Sen. Sherrod Brown, D-Ohio, speaks during a Senate Commerce, Science, and Transportation Committee hearing on improving rail safety in response to the East Palestine, Ohio train derailment, on Capitol Hill in Washington, March 22, 2023. (AP Photo/Manuel Balce Ceneta, File)

U.S. Sen. Jon Tester, D-Mont., leads a cheer at a rally with Planned Parenthood Action Fund President Alexis McGill Johnson, Thursday, Sept. 5, 2024, in Bozeman, Mont. (AP Photo/Matthew Brown)

Republican U.S. Senate Candidate Tim Sheehy speaks to supporters during an event at the Northern Hotel, Wednesday, Sept. 4, 2024, in Billings, Mont. (AP Photo/Matthew Brown)

FILE - Chairman Sherrod Brown, of Ohio, speaks during a hearing on Capitol Hill, Dec. 6, 2023, in Washington. (AP Photo/Alex Brandon)

Montana Republican U.S. Senate candidate Tim Sheehy, left, and U.S. Sen. Tom Cotton, R-Ark., listen to a supporter at a campaign event at the Northern Hotel, Wednesday, Sept. 4, 2024, in Billings, Mont. (AP Photo/Matthew Brown)