Marco Rubio was a bundle of nervous energy as he waited his turn to speak about the bipartisan immigration plan he had helped to draft.

The Republican senator from Florida clasped his hands in front, then in back, then in front again. He poked his tongue into his cheek, he clenched his jaw, and he licked his lips. He fiddled with his suit-jacket button once, then again, then a third time. He rubbed his fingers together, then interlocked them.

His anxiety was understandable: Rubio, one of the Republican Party's hottest presidential prospects for 2016, was about to make official his support for allowing undocumented immigrants to become legal – the dreaded "amnesty" that is poison to many a Republican primary voter.

But when his turn came to speak in the Senate TV studio, Rubio gripped the lectern with both hands and talked in a strong, confident voice about the need to "address the reality" that there must be a path to legitimacy for illegal immigrants.

"We are dealing with 11 million human beings who are – who are – who are here undocumented, the vast and enormous majority of whom have come here in pursuit of what all of us would recognize as the American dream," he said.

In English, and then in Spanish, he recited his well-known credentials on the subject. "I am clearly new to this issue in terms of the Senate," he said. "I'm not new in terms of my life. I live surrounded by immigrants. My neighbors are immigrants. My family is immigrants. Married into a family of immigrants. I see immigration every single day. I see the good of immigration."

Eight senators – four Democrats and four Republicans – agreed on the principles outlined Monday for comprehensive immigration reform. But while the group was led by Sens. Chuck Schumer, D-N.Y., and John McCain, R-Ariz., the one who matters most to the success of this latest immigration effort is Rubio.

Rubio has strong credentials among the tea party faithful, and he is mentioned as the top 2016 presidential choice by some of the most conservative elements of the GOP. His willingness to risk both of these is an admirable act of political bravery.

Republicans, unnerved by the drubbing Mitt Romney received from Latino voters, are gradually moving toward the realization that they've got to drop their no-amnesty absolutism. But the type of voters who dominate the Republican presidential primaries are not necessarily on board with the change. McCain had to harden his position considerably to win the nomination in 2008, and Romney battled with his primary rivals over who would be the toughest on illegal immigrants.

For Rubio, the safer course would be to keep quiet about his support for what conservatives call amnesty – as Rep. Lamar Smith, R-Texas, did Monday. "By granting amnesty, the Senate proposal actually compounds the problem by encouraging more illegal immigration," he said in a statement.

Rubio's refusal to be cowed by Smith and his ilk will probably get the attention of House Republicans who would otherwise block the Senate plan.

It certainly got the attention of the news media. There are seats for 24 in the Senate TV studio, but there were 110 people in the room before the senators and their staffers arrived. No fewer than 21 TV cameras, and a bilingual cacophony, awaited the lawmakers.

Rubio was the last of five senators to take the stage (the other three didn't participate) and the last to talk. He listened as Schumer, a fiercely partisan Democrat, observed of McCain and Rubio: "By their presence today, my Republican colleagues are making a significant statement."

Finally, after Sen. Bob Menendez, D-N.J., delivered a long, grandstanding statement in Spanish, Rubio got his turn. "First of all, let me just say, John, I don't agree with anything he just said about you in Spanish," he joked to McCain. He then spoke about his life and made a conservative pitch for a policy that is anathema to many of his fellow conservatives. "We need to be honest with ourselves about how important immigration is for our economy," he said.

In the questioning that followed, a reporter asked Rubio to elaborate on his support for the new proposal, which goes well beyond his previous immigration efforts. "We have to deal with the people that are here now in a way that's responsible but humane, and this does that," he said.

It's unclear whether Republicans are ready to hear such a message. But Rubio is courageous to try.

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