Alme won the nomination, NBC News projects, after a late launch following GOP Sen. Steve Daines' last-minute retirement, sparking criticism that Daines picked his successor.
Employed at a National Institutes of Health lab in Montana, the two allegedly brought deactivated virus from the Republic of the Congo without a permit.
Senator Steve Daines withdrew his candidacy for re-election moments before the filing deadline, and then endorsed Kurt Alme in what appeared to be a coordinated swap to preclude competition.
Voters in California, Iowa, Montana, New Jersey, New Mexico and South Dakota cast ballots on Tuesday in primary elections ahead of the 2026 midterm general election in November.