In addition to Rubio, the gang members not on the Judiciary Committee are McCain and Democratic Sens. Robert Menendez of New Jersey and Michael Bennet of Colorado.
The knowledge that the Gang of Eight would object caused some proposals to wither without a vote.
Sen. Richard Blumenthal, D-Conn., prepared two gun-related amendments, but he had only one of them debated and withdrew it without a vote he was certain to lose.
On the other hand, amendments that the Gang of Eight decided didn't threaten their measure or might strengthen it rose or fell based on other factors. The phasing in of the biometric system, a Republican suggestion, was a key one.
Hirono deferred on several of her proposals but chose a different course on a proposal to let U.S. citizens suffering from extreme hardship petition for a sibling or adult married child to immigrate.
"This is a tiny change and would be utilized only in the most sympathetic cases," she said. She noted that as drafted, the legislation eliminated an existing preference for siblings eager to follow family members to the United States, a category that historically has tended to benefit immigrants from Asian nations.
"I understand that my amendment is in conflict with the agreement that the Gang of Eight reached on this bill," she said, adding, "If they were not part of the Gang of Eight, I believe they would support this limited amendment."
In the debate that followed, two nongang Democrats on the committee, Sens. Al Franken of Minnesota and Chris Coons of Deleware, said they would support Hirono.
But Graham said an issue of overriding importance to him had been the bill's establishment of a new system for legal immigration. "What I'm trying to do is have a family component within a merit-based immigration system, not turn immigration into chain migration family-based immigration.... And I will continue to insist on that for my participation," he added.