Sen. Susan Collins, R-Maine, said Thursday she will not back former President Donald Trump if he wins the Republican nomination, NBC affiliate News Center Maine reported.
While the longtime Republican senator did not officially endorse another candidate in the primary, she said she's happy former U.N. Ambassador Nikki Haley is still in the race.
Collins has been in office since 1997 and has often been seen as a moderate Republican whose Senate vote can be pivotal.
Following the Jan. 6, 2021, attack on the U.S. Capitol, Collins joined six other Republicans in voting to convict Trump of incitement of insurrection after his second impeachment.
"Instead of preventing a dangerous situation, President Trump created one," she said at the time. "And rather than defend the Constitutional transfer of power, he incited an insurrection with the purpose of preventing that transfer of power from occurring.
However, she voted to acquit him at his first impeachment trial in 2020, when he was charged with abuse of power and obstruction of Congress, saying she hoped Trump "learned his lesson." Former Massachusetts Gov. Mitt Romney was the only Republican senator to cross party lines in that case.
When Trump ran for the first time in 2016, Collins said she would not endorse him. In 2020, she didn't make an endorsement during the race, but broke with Trump and others who denied the results of the election, congratulating Joe Biden after he won.