W ASHINGTON—Centrist Sen. Thom Tillis (R., N.C.) said he won’t seek re-election in 2026, less than 24 hours after he voted against a motion to advance President Trump’s tax and spending megabill, drawing public backlash from the president.

A popular former Democratic governor, Roy Cooper, is expected to announce a bid this summer. The Republicans are banking on an endorsement by President Trump to clear their field.

Donald Trump on Tuesday floated his daughter-in-law Lara Trump as a possible replacement for U.S. Senator Thom Tillis, who will not seek reelection in North Carolina after clashing with the U.S. president over his tax-cut and spending bill.