(CNN) For about an hour, no one was sure what was going to happen to break a tie vote to end debate on the next NASA administrator.
Usually Vice President Mike Pence makes his way through the US Capitol to break the tie -- but he was at Mar-a-Lago with President Donald Trump, so that seemed impractical.
Then GOP Sen. Jeff Flake of Arizona returned to the floor and changed his "no" vote to "yes" for GOP Rep. James Bridenstine to be the next NASA administrator.
The motion then passed on a partisan 50-48 vote. Flake, a vocal critic of the President's, had been the only Republican to vote against Bridenstine.
Both Sen. John McCain, an Arizona Republican, who is ill, and Illinois Democratic Sen. Tammy Duckworth, who just had a baby, were absent.
After the vote, Sen. John Cornyn of Texas, the Senate GOP whip, was asked about Flake's vote change.
"He has an issue he wants to talk to (CIA) Director (Mike) Pompeo about. He was looking for assurances he would have that opportunity and I'm confident he will have that chance this afternoon," Cornyn said. "I think there are some issues related to travel restrictions to Cuba."
Flake later told CNN he had submitted questions to Pompeo after his confirmation hearing to be secretary of state and added, "I'm still waiting for satisfactory answers."
Flake, who is a member of the Foreign Relations Committee and whose vote is significant, said he is still undecided on how he will vote on Pompeo's nomination and indicated he "still has some issues."
Separately, Flake said he has problems with Bridenstine and at one point had a "hold" on his nomination.
"I wasn't enthusiastic about him but that wasn't the point," Flake explained.
The party-line vote against Bridenstine reflects the steep opposition from Democrats about Trump's nominee to head the space agency, who they believe is not a "space professional" in the words of Sen. Bill Nelson, a Florida Democrat. One Republican, Sen. Marco Rubio of Florida, had previously expressed concerns about Bridenstine but voted for him in the end.
Democrats also complained about his views on climate change.
"NASA is one of the few remaining areas that has largely avoided the bitter partisanship that has invaded far too many areas of government and our society today," Nelson said in a floor speech.
When he was nominated, Sen. Ted Cruz, R-Texas, called Bridenstine a "strong, principled and effective leader" who will "work hard to advance our national space policy goals, expand human space exploration and secure America's leadership in space."
A final confirmation vote for Bridenstine is expected Thursday.