Noorani says the Senate pair is helped by united support from business, law enforcement and religious leaders at the grassroots level.
"It comes down to the fact that leaders in key districts who own a bible, wear a badge or own a business are pressuring their Republican members of Congress to get behind immigration reform," he says.
Johnson says the combination of McCain's experience and Rubio's political appeal may just be what wins over support from otherwise uninterested House Republicans.
"They seem to represent the old guard and the new guard on this," he says. "McCain's got the experience of having gone through this meat-grinder … And I think Rubio reflects the new face of the Republican Party, the fiscal conservatism and the limited government with the shifting demographics of the emerging Latino vote. That's a hell of a twofer."