Republican senators are poised to block any witnesses from testifying in President Donald Trump's impeachment trial.
The vote to block witnesses is scheduled for Friday.
On Thursday night Sen.
Lamar Alexander announced he'll vote "no" on the motion.
Alexander's decision gives cover to vulnerable GOP senators.
Maine's Susan Collins and Alaska's Lisa Murkowski said they'll vote "yes" on witnesses.
Democrats need four Republican votes to reach a 51-vote majority and pass the motion.