Sen. Marco Rubio, R-Florida, made the rounds Sunday morning, appearing on nearly every talk show. He discussed immigration, impending gun-control legislation, and his criticism of Beyonce and Jay-Z’s trip to Cuba. (Nicki DeMarco/The Washington Post)

After years of false starts, the Senate appears ready to introduce a bipartisan immigration bill this week — a piece of legislation that has massive policy and political implications attached to it.

A bill being introduced isn’t the same thing as a deal that passes the Senate, of course. Sen. Marco Rubio (R-Fla.), a member of the bipartisan “Gang of Eight” crafting the legislation, acknowledged as much in an interview Sunday on NBC’s “Meet the Press.”

“It is not the take-it-or-leave-it offer,” he said. “It is a starting point of reform.”

Below is our look at five senators who will have a major role to play in whether the bill will make it to the finish line and what it will look like if/when it does. (Senators are listed in alphabetical order.)

John Cornyn : What the Texas Republican does will be fascinating for three reasons. First, he is up for reelection in 2014 and has to be mindful of how his now-colleague Ted Cruz upset the establishment pick in a Republican Senate primary in 2012. Second, the issue of immigration is obviously a pressing one in the Lone Star State — with strong voices both for and against reform. Third, Cornyn is the second-ranking Republican in the Senate and could well be a window into how the party’s leadership views the legislation and the political and policy issues surrounding it.

Bob Menendez : The New Jersey Democrat will be a barometer of whether the bill is aggressive enough for liberals in the Senate to support it. Menendez, who like Rubio is Cuban American and a member of the Gang of Eight, sounded an optimistic note in an interview Sunday with Star-Ledger editorial columnist Linda Ocasio. “This bill might not have been the one I would have written,” he said. “But it is the art of the possible.” If Menendez stays on board, he’ll bring along other liberals who have concerns about the money being spent on border security. If he walks, so will they.

Rand Paul : If the first three months of the 2013 Congress have proved anything, it’s that the Kentucky Republican with one eye squarely on the 2016 presidential race has a real ability to influence issues and debate in Washington. (See drones.) In a speech to the U.S. Hispanic Chamber of Commerce last month, Paul seemed open to a comprehensive overhaul although pointedly did not use the phrase “path to citizenship,” which is sine qua non for Democrats when it comes to the broader bill. (Paul is apparently for a path to normalization, not a path to citizenship.) If he signs on to whatever the final bill looks like, Paul will provide significant cover for conservative Senators wary about voting in favor of something that a significant chunk of their GOP constituents oppose.

Mark Pryor : The Arkansas Democrat is up for reelection in a very red state — President Obama lost it by 23 points in 2012 — and will be very mindful of concerns that this bill rewards those who entered the country illegally. (If you haven’t bought stock in the word “amnesty,” now would be a good time to do so, because you are going to hear it a lot over these next weeks and months.)

Rubio: Yes, the senator from Florida gets lots and lots of attention on the immigration bill. (He was on seven — yes, seven! — talk shows on Sunday.) But, in this case, the attention is warranted. Rubio not only is Cuban American but also represents a state where immigration is a top-of-the-mind issue. And then there is the fact that he is widely regarded as the front-runner for the 2016 Republican presidential nomination. It’s no exaggeration to say that if Rubio walks away from the final product on immigration, the bill might not make it.

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