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