He stepped up in the Senate as the co-author of a bipartisan immigration reform bill that would have provided a pathway to citizenship for immigrants in the US illegally.
But he soon came under withering criticism from the party's ultraconservative tea party wing. The Senate passed the bill, but it failed in the House.
In a moment of candor, Rubio remembered the months of trying to get back up as "a real trial for me." He now says the bill does not have the support to become law and the first focus should be on border security, a standard Republican position.
Others, too, have shifted on the matter. In 2013, Wisconsin Gove. Scott Walker said it "makes sense" to offer a way to citizenship for immigrants in the country illegally.
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Earlier this month, however, he said he no longer supports "amnesty."
Complicating that switch, Walker recently discussed immigration with party leaders in New Hampshire, a key early voting state in presidential nominating contests.
One of them, state leader Jennifer Horn, says that Walker favored legal status, a position many conservatives equate with "amnesty."
Worse for Walker, The Wall Street Journal reported Thursday that he actually said he favored a path to citizenship, though Horn denies Walker said that.
Rubio and Walker are not alone in embracing an immigration overhaul at some point. But doing so raises the specter of "amnesty" in the minds of those who want people unlawfully in the country to be given no relief from the threat of deportation.
"All the candidates have mixed statements they have statements that seem to support amnesty and they all have ones that seem to oppose it," said Roy Beck, executive director of Numbers USA, which seeks to reduce immigration.
"They're torn between the big-money people who gain from high immigration and the voters who oppose it.