The whip has Reid’s back:

“It’s a zero-sum situation,” said Durbin, who is in charge of counting votes in the Senate. “If we thought that just putting the trigger in meant that we’d end with 61 votes,” he explained, then that’s what leadership would have done.
“But there were some [senators] that felt that that just didn’t go far enough moving toward a public option,” said Durbin, who is himself a backer.
“We have 60 people in the caucus,” Reid said. “We’ll all hang together and see where we come out.”
…
Durbin said that he is confident the progressive wing in the Senate is satisfied with the opt-out compromise.