The prospects for immigration reform rest on a simple question: Are Republicans prepared to accept reform that includes a path to citizenship without hard border security triggers as necessary pre-conditions for it to proceed, or aren’t they?

Marco Rubio — who is being closely watched by Republicans for cues on immigration — has offered a new interview on the Hugh Hewitt show that has given advocates reason for optimism. They think Rubio’s remarks suggest a route to a compromise Democrats might accept.

Senator John Cornyn is trying to shove reform to the right by insisting that hard border security metrics be met before any provisionally legal immigrant can be granted a green card and then embark on the path to citizenship. That is unacceptable to Democrats who believe it sets the stage for manipulation of those metrics with the deliberate goal of sinking citizenship. In his comments, Rubio noted that he and Republicans are working on another amendment that would strengthen border security in the gang of eight bill — yet he also seemed to stake out a middle ground of sorts:

“I don’t want to leave the border plan up to the Department of Homeland Security and Janet Napolitano. That is a mistake that is in the current bill. I think what we need to do is detail minimum standards, at a minimum what the border plan should be, and detail it. It must have this…That’s what we’re working on accomplishing.”

The reason Rubio’s comments are important rests on a very fine, but crucial, distinction. The “gang of eight” compromise stipulates that DHS come up with a plan to secure the border, and that billions be allotted for border security. Rubio seems to be proposing to mostly take the border plan out of the hands of DHS, and that Congress lay out more specific “standards” and “details” the border security plan must contain. That is different from what Cornyn is proposing: That specific security metrics must be reached after 10 years as a pre-condition for citizenship to proceed. Democrats can probably accept some version of the former. They cannot accept the latter.

We need to see the details of Rubio’s amendment before getting too optimistic. But Frank Sharry, the head of America’s Voice, says Rubio’s comments suggest a subtle effort to marginalize the Cornyn-led “hard trigger” camp by coming up with a new way of adding more border security to the bill that enough Senators (not including the hard-trigger diehards and far right conservatives, obviously) can ultimately agree on.

“This suggests to me that the adults have stepped in, marginalized Cornyn, and are negotiating a border security amendment that doesn’t threaten the path to citizenship,” Sharry emails me. “What Rubio is saying here, and what we are fine with, is that members of Congress want to specify how the initial $4.5 billion in border security money is spent, rather than leaving it to DHS.”

Of course, as I noted here the other day, the Cornyn approach (hard-triggers) is deliberately designed to be very hard for Republicans not to support, because if they don’t, they are exposed to criticism from the right. And indeed, right on cue, Politico reports that a number of on-the-fence Republican Senators are jumping aboard the Cornyn “hard trigger” train. That could kill reform.

Bottom line: Success may turn on whether a space can be carved out here where enough Republicans can accept citizenship in exchange for a more direct say over what the border security plan will look like, rather than for “hard triggers” that would be required to set it in motion — and on whether Rubio is serious about carving out that space.

* CONGRESS’ SKEWED PRIORITIES ON NSA PROGRAMS: Key news of the day: Top Senators are now considering taking Congressional action to limit the access that private contractors (such as the one employed by Edwards Snowden) have to highly classified data, in response to the leaks about the NSA programs. Whatever the wisdom of this move, by contrast, it’s striking how little discussion there is among top officials of any measures that would bring a bit of transparency to these programs so the public can adequately debate them.

* WHY A “DEBATE” OVER NSA PROGRAMS IS IMPOSSIBLE: Senator Ron Wyden, who has persistently warned of the perils of surveillance overreach, sums it up in an interview with the Post’s Ruth Marcus:

 “You can’t have much of a debate with the public if there’s that big a gap between what the public thinks a law means and how the executive branch is interpreting it.”

Wyden is referring to the Patriot Act. At a minimum, we need more transparency here as to how the FISA court is interpreting it in the process of green-lighting the government’s requests for authorization of broad surveillance.

* HAVE GUN TALKS RESTARTED IN THE SENATE? Jonathan Weisman reports that quiet discussions have started involving two senators who voted No on Manchin-Toomey — GOPer Kelly Ayotte and Dem Mark Begich — though both adamantly deny any chance of a change in their votes. The talks supposedly center on tweaks to the bill that would clarify even further that the measure would never create a gun registry.

Manchin-Toomey strengthened prohibitions against any registry, so it’s unclear whether any assurance would be enough; feigned fears of registration were the excuse, not the reason, for opposing the measure. But it’s good that senators are getting prodded to rethink (and justify) their No votes, and this issue certainly will come up again eventually.

* THE SIX-MONTH ANNIVERSARY OF NEWTOWN SHOOTING: It’s today, and Gabrielle Giffords marks it with an Op ed piece in the Newtown Bee:

Our country, we know, is with us. Americans in every state support common-sense solutions to reduce gun violence. Congress is out of step with their constituents by not immediately passing these measures that will save lives. Without them, people will be killed who would otherwise live.

One test of the power of the new, emerging infrastructure to combat the NRA will be its ability to keep the need to combat gun violence in the headlines. Giffords’ efforts underscore a newfound determination not to let the public forget, as has happened after so many other mass shootings.

* OBAMA UNDER PRESSURE ON GAY RIGHTS: Peter Wallsten has a fascinating look at the very difficult dilemma Obama will face if the Supreme Court strikes down the Defense of Marriage Act:

The question for Obama turns on whether the federal government should extend full benefits to gay couples living in states that don’t recognize their marriages. Obama would face rare, concrete decisions on the politically combustible question of same-sex marriage — an area he has largely left to the purview of courts and state legislatures.

In this case, Obama would have to decide whether the federal government has the authority to recognize gay marriage in a state where it’s illegal. It’s the basic tension that won’t go away until full equality is realized everywhere.

* ED MARKEY IN DRIVERS SEAT IN MASSACHUSETTS RACE: Scott Conroy has a good overview of the race that explains why Ed Markey appears to be dominating Gabriel Gomez: Markey is successfully driving a wedge between Gomez’s Republican positions and the Democratic Massachusetts electorate; and there is no single galvanizing issue (like health care in 2010) to drive an upset like the one Scott Brown pulled off. The Real Clear Politics average of polls puts Markey up by 9.3 points.

Also: Markey today picks up the endorsement of Massachusetts’ largest Spanish language newspaper, which argues Markey would be better for Latinos than Gomez, the son of Colombian born immigrants.

* AND OTHER PLUM READS:

* Paul Krugman on how America’s best hope for maintaining a middle class society may turn on a strong safety net funded by higher taxes on capital income and investment.

* Political scientist John Sides responds to my question. Answer: Ultimately, the GOP really may not have to rebrand itself or moderate on key issues to remain competitive in future national elections. But the GOP’s refusal to modernize could matter in races for marginal Senate seats.

* Steve Benen on the decision by the GOP governor of Nevada to veto a sensible expansion of background check laws supported by the state legislature and a great majority of his constituents — ostensibly in the name of protecting their rights.

* Jay Rosen on how Glenn Greenwald’s NSA scoops validate the project of opinion-driven reporting, or as I like to call it, opinionated reporting.

What else?

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.