Rep. Roger Marshall won the Kansas Republican Senate primary on Tuesday evening, beating former Secretary of State Kris Kobach and a slew of other candidates,AP reports.

Why it matters: Following GOP Sen. Pat Roberts' retirement announcement, some Republicans worry that if Kobach won the primary it would endanger the party's chances of keeping the seat and maintaining a majority in the Senate.

What's next: Kobach will face off against Democratic state Sen. Barbara Bollier — who won the Democratic primary Tuesday — in the general election.