Republican Tim Sheehy bolstered the GOP's newly acquired Senate majority with a victory over three-term Democratic U.S. Sen. Jon Tester in a contest of national importance that featured a record-setting torrent of spending by the two sides.

Tim Sheehy, a wealthy Republican businessman, was dogged by controversies during the campaign. But Senator Jon Tester, a Democrat, could not outrun the demographic shift in his deep-red state.