Perhaps the move by a handful of Senate Republicans and Democrats to press ahead on a compromise immigration reform package will not surprise many observers. The rationales on both sides are clear. President Barack Obama got some backlash during the presidential campaign from Latino voters, who responded to his promise of immigration reform in a second term by reminding Obama that he promised the same thing before his first term, and totally failed to deliver. Democrats have wanted to press forward on normalization for existing illegal immigrants for years, hoping to reap the benefit of the additional voters in years ahead. Republicans, who have balked at reform in part for that reason, saw the changing demographics of the electorate in 2012 and knew they needed to address the issues or risk being shut out of a key bloc of current voters for the foreseeable future. And now, Sen. Marco Rubio, who I interviewed yesterday, is at the heart of this fledgling deal.

The surprise, if there is one, is that compromise arrived so quickly. The Gang of Eight on immigration rolled out their conceptual plan on Monday, just a week after Obama's inauguration. For the last two years, Congress has been singularly unable to reach broad compromises on nearly any issue. The Senate hasn't even produced a normal budget since April 2010, their most basic responsibility, thanks to a failure of leadership and a desire to maintain financial-crisis levels of federal spending without accountability or formal dissent. Neither the Senate nor the House has produced a workable compromise on immigration since 1986, a bill that Republicans mainly remember for a broken promise by the Democratic-controlled Congress to address border security after Ronald Reagan signed off on a general amnesty.

With that history of dysfunction, any agreement among even a small number of Republicans and Democrats on Capitol Hill seems surprising. Even with the stakes high for both parties, as they have been on taxes, spending, and the debt ceiling, this current political class has been more interested in deducing how to exploit problems than in finding solutions to them.

And at least conceptually, the plan looks like a real compromise, with all sides being able to claim some victories, and all sides conceding on long-standing points of principle. Democrats gained a path to citizenship through normalization of most existing illegal immigrants. Republicans won on a process that puts those applicants behind those already in line for immigration, plus fines, background checks, and a bar on federal welfare resources. A new guest-worker program to supply low-cost labor will eventually emerge, and so will enhanced requirements for employer verification of new hires. The bill addresses border security and visa programs that have long been dysfunctional, requiring their reform as a trigger to proceed with normalization as heretofore illegal immigrants register with the government and bring their economy out of the shadows.

Or will those reforms be required? The proposal as released promises that a commission will review the implementation of security measures on border security and visa reform, a panel composed of governors and attorneys general of states along the southwestern border — a new twist meant to assure border hawks of the seriousness with which the Senate will take the border-first approach. That implementation will take place simultaneously with initial registration of currently illegal workers and their families. Once these people are registered and cleared, the U.S. will not take any more enforcement actions against them, and can proceed to the next step when the commission "makes a recommendation" that the security measures have been fully implemented. 

However, "makes a recommendation" sounds suspiciously vague and weak, especially to conservatives who fear a repeat of the 1986 debacle. No one on the Gang of Eight seemed prepared to commit to whether this was a strictly advisory panel with no real authority to stop the normalization process, or a robust trigger that would force the federal government to satisfy the border states on enforcement. Jay Carney at the White House refused to give his own interpretation, kicking it back — wisely — to the Gang of Eight by noting that "we have not seen any legislative proposal."  

At least one member of the Gang of Eight went on the record about the trigger, or at least his concept of it. Sen. Marco Rubio is a junior member of the group, but perhaps its most critical vote. John McCain and Lindsey Graham have pushed immigration reform for years, and have little draw among Tea Party conservatives in the GOP. Rubio, on the other hand, won his Senate seat by riding that grassroots wave to a victory over the GOP establishment in the 2010 Florida primary, and then a resounding victory in the general election. Seen as the future of his party and a frontrunner for the 2016 presidential nomination, the last thing Rubio wants is to be the cause of a split within the party.

Yesterday, I spoke with Rubio about the proposal, and specifically about the trigger. "That's one of the issues we have to work on," Rubio said. "What was announced today was a set of principles." Rubio explained that it will take a few weeks to move those principles into specific legislative language, but when that happens, the trigger has to work to make enforcement take priority. "I can tell you that based on my principles," Rubio asserted, "I will not be supporting any law that does not ensure that the enforcement [prerequisites] happen, because I don't want to be here in five or 10 years dealing with this again." Otherwise, we will end up encouraging more people to flood into the U.S. illegally over the next few years, Rubio explained, while referencing what happened in 1986. "This is only worth doing if we ensure that this doesn't happen again."

Just to be sure, I asked the question a second time at the end of the interview. "You are committing that without an enforcement mechanism that requires the border security and the visa reform to be in place and be effective and certified by a commission in some sense, you are not going to go forward with the rest of this package?" 

"I'm not going to support anything and I don't want us to do anything," Rubio replied, "that brings us right back to this point again in the future. And that's why that we have to make sure that the way this law is structured, [it] ensures — guarantees — that the enforcement things happen.... Yes. That's absolutely one of the key standards I bring, it's one of the key parts of our principles."

That at least puts Rubio on the record as expecting that this package will require some sort of trigger to proceed with normalization that "guarantees that the enforcement [provisions] happen" first. That presents a problem for the other seven members of this group, if the final legislative language does not include those guarantees. If the trigger is real and has teeth, Rubio's support could move a significant number of Republican votes in the Senate, and put pressure on House Republicans to finally put this issue to rest.  

If Rubio peels off and announces his opposition to the effort, though, all bets are off. The Senate might still pass immigration reform, but they won't find many Republicans other than McCain and Graham for cover; Jeff Flake could follow Rubio out of the deal under those circumstances. Without Rubio (and especially without both Rubio and Flake), the deal will go exactly nowhere in the House, which will only act on the bill if it gets substantial Republican support in the upper chamber first. John Boehner will have a tough time on this package as currently composed even with Rubio's support. Without Rubio, it might prompt a real leadership fight, and Boehner's unlikely to test out his standing to push through a proposal with the stench of 1986 on it, regardless of Democratic support.

In other words, stay tuned for the legislative language to see just how tough that trigger will be. Rubio will be the key to the success or failure of the compromise, and he will come under tremendous pressure from his base to ensure the best possible outcome from compromising on normalization. His future — and the confidence of the electorate in Congress' ability to solve big issues — will hinge on whether his partners are willing to deliver those guarantees in exchange for their own benefit. If not, the specter of 1986 may return to haunt another Republican leader.