U.S. Senator Lamar Alexander (R-TN) speaks to reporters as he exits the Trump impeachment trial in Washington, U.S., January 30, 2020. REUTERS/Brendan McDermid

WASHINGTON (Reuters) - Republican Senator Lamar Alexander said on Thursday that he would vote against calling witnesses in the impeachment trial of President Donald Trump, dealing a blow to Democrats who had hoped to hear from current and former top Trump aides.

Alexander was one of a handful of Republicans that Democrats had hoped would side with them to reach a 51-vote majority necessary to call witnesses and subpoena other evidence.