WASHINGTON—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.

North Carolina Republican U.S. Sen. Thom Tillis made an unexpected decision not to seek a third term. Here's what the reaction has been.