Minutes before the Senate filing deadline, Senator Steve Daines withdrew his re-election bid and an ally jumped in. Even some fellow Republicans criticized the 11th-hour switch.
Kurt Alme, who has been serving as the U.S. attorney for Montana, was endorsed by Senator Steve Daines and President Trump to succeed Mr. Daines in a race for what will now be an open seat.
Even as some top targets held on, lawmakers in both parties were pushed into runoffs by challengers in Texas, while some in the North Carolina state legislature lost.
The surprise announcement by Senator Steve Daines could give Democrats a slim opening in the Republican-leaning state in their uphill fight to take the Senate majority.