Sen. Mitt Romney makes it official: He’ll vote with Democrats to call witnesses in the Senate trial on two articles of impeachment against President Trump.

“For those asking: As [Sen. Romney] has said, he wants to hear from Ambassador Bolton, and he will vote in favor of the motion today to consider witnesses,” Liz Johnson, a spokeswoman for the senator, wrote on Twitter on Friday.

For those asking: As @SenatorRomney has said, he wants to hear from Ambassador Bolton, and he will vote in favor of the motion today to consider witnesses. — Liz Johnson (@LJ0hnson) January 31, 2020

Romney joins Sen. Susan Collins (R-MN) in supporting the Democrats’ call for witnesses. That means the latest tally is 50 against, 49 for — with Sen. Lisa Murkowski (R-AK) the last hold out.

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With the Utah Republican’s decision, everything’s up in the air. If Murkowski joins Romney and Collins, the vote would be 50-50. It’s unclear whether Supreme Court Chief Justice John Roberts, who is presiding over the trail, will step in to break a tie. Republicans have been predicting that Roberts will not break a tie, which would cause the motion to call witnesses to fail. But no one knows for sure.

Sen. Lamar Alexander (R-TN) announced on Thursday that he will vote against allowing more witnesses.

“I worked with other senators to make sure that we have the right to ask for more documents and witnesses, but there is no need for more evidence to prove something that has already been proven and that does not meet the U.S. Constitution’s high bar for an impeachable offense,” Sen. Alexander said. “There is no need for more evidence to prove that the president asked Ukraine to investigate Joe Biden and his son, Hunter; he said this on television on October 3, 2019, and during his July 25, 2019, telephone call with the president of Ukraine.”

So all eyes are on Murkowski now.