“His comfort zone has always been more of the Reaganesque optimist, and that is what endeared him to Republicans as a potential nominee,” said longtime strategist Alex Castellanos, who launched NewRepublican.org to help get his party on track. “When Rubio looks like an inside-Washington deal-cutter or an emblem of the ‘party of no,’ either one of those undermines his greatest strength, which is exactly what the party needs right now: optimism and vision.”

But Rubio’s path is unclear, confounding even some of his longtime allies. This week, as hundreds of business, faith, and law-enforcement leaders kicked off a massive, last-ditch lobbying effort for immigration reform, American Conservative Union Chairman Al Cardenas called Rubio’s retreat from a comprehensive approach “unproductive.”

“I don’t understand it,” said Cardenas, a former chairman of the Florida Republican Party and Rubio’s onetime mentor. “I wasn’t pleased with it.”

Rubio’s team says the senator is simply trying to keep the bill moving and find common ground with House Republicans, who have refused to vote on the Senate’s comprehensive legislation. “Senator Rubio is just being realistic about what’s possible in the current political environment,” said Alex Conant, Rubio’s press secretary. “It’s not realistic to believe that the House is going to take up and pass the Senate bill.”