"I think comprehensive reform is doable," Arizona Republican Senator Jeff Flake said, another member of the group. "We wouldn't be in this if we didn't think we could do it."
Some have been down this road before. New York Democrat Chuck Schumer and South Carolina Republican Lindsey Graham, agreed on a comprehensive plan in 2010 only to see it unravel. Senator John McCain of Arizona, working with the late Massachusetts Democratic Senator Edward Kennedy, tried unsuccessfully in 2005 and 2006.
But after the 2012 election in which Democrats won the Hispanic vote nationally by 70 percent, Graham said he sensed a new imperative.
The morning after the election, Graham called Schumer and said, "I want to get the band back together and McCain wants in."
Graham explained in an interview what prompted his call.
Democrats, including Obama, had long promised Hispanics some action on immigration.
"The reality from the Republican point of view is that we had to get this issue resolved," Graham said. "So we Republicans had a need and Democrats had a need," which equaled an "an opportunity to get it done."
Until late last year, Schumer and McCain, who have been in Congress together for three decades, had rarely spoken to each other. The chill between them eased a bit in January when they ended up as a part of a group of lawmakers who reached a deal on new Senate rules to ease gridlock.
"We bonded," said Schumer, "and then moved to immigration."
McCain brought in Durbin, with whom he grew close in 1983 when both were newly elected members of the House of Representatives.
Durbin had made friends with freshman Republican Rubio in predawn workouts in the Senate gym. Durbin invited Rubio.
"I told Marco: 'I think you should be part of this. What do you think?" Durbin recalled. "He said: 'I think I can work with you. At least I'm willing to try.'"
TALKING TO THE HOUSE
The senators have been meeting two to four times a week since December, each session focusing on a mutually agreed-upon agenda. They sit in a circle with 20 staffers behind them, aides said.
"Everyone in there wants to get it done," said Flake. "No one is looking for scoring political points. That makes all the difference."
"There have been hard and tough negotiations, but it has been done all in the spirit of achieving the goal, in which compromise has been made on both sides," said New Jersey's Democratic senator, Robert Menendez, another group member.
A group of eight House members - also four Democrats and four Republicans - began working on its own plan years ago, long before the Senate group even formed.