Montana State Auditor Matt Rosendale will challenge Democratic U.S. Sen. Jon Tester in November as Republicans look to take back Tester's seat and complete a sweep of Montana's congressional delegation.

In Montana's other top primary, former state legislator Kathleen Williams defeated four other candidates to win the Democratic nomination for the state's U.S. House seat and take on Republican incumbent Greg Gianforte. Her win punctuated a big night for women running for office in the eight states that held primaries on Tuesday.

Republicans have been gaining ground on Democrats holding federal and statewide offices in every Montana election since 2010. Two years ago, GOP candidates won every statewide race except the governor's office, which Gianforte lost to incumbent Democrat Steve Bullock.

Republicans hope to finish taking over Montana's federal offices by defeating Tester, whom President Donald Trump has attacked for releasing misconduct allegations that derailed his nominee to head the U.S. Department of Veterans Affairs.