That’s because in recent days, one of the chief Republican gang of eight members, Sen. Marco Rubio (R-Fla.), has soured on the bill, citing insufficient border security measures. In private conversations, Rubio has been making entreaties to try give the bill a more conservative bent, according to sources.

Rubio had privately urged fellow Republican Sen. Kelly Ayotte (R-N.H.) to remain quiet about her support for immigration reform, in hopes that Senate negotiators would amend the bill’s border security measures to win her vote, according to three sources, including one Republican Senate aide. Ayotte, a moderate-leaning New Hampshire Republican, decided nevertheless to announce her support for the measure on Sunday, becoming the first Republican outside of the group to back the reform legislation.

Rubio “has not been telling them to vote no,” said one Senate Democratic aide familiar with negotiations. “He has been apparently holding people back from declaring support for the bill, while at the same time saying the bill needs changes in order to garner support. My understanding is he told Sen. Ayotte’s office to hold back, but she didn’t care.”