Sometime this week, House Republicans are expected to roll out a statement of principles on immigration reform, and most reports suggest some sort of embrace of legalization for the 11 million will be in the mix. Byron York even reports that Republicans appear to be treating the possibility that they will act on reform seriously, because some have decided that only opposing Obama on everything isn’t enough, and the GOP “has to be the party of alternatives.”

That’s great to hear! And it is is a real step forward that Republicans are now apparently embracing legalization, at least in principle.

But there’s a very simple way to know whether Republicans are serious about reform, and actually want to get to Yes, or whether they are simply trying to demonstrate a willingness to do something, so they don’t appear captive to the nativist base, while laying the groundwork to blame failure on Dems later.

Here’s the question: What will Republicans demand as a condition for legalization?

If their basic principle is that legalization will be contingent on undocumented immigrants paying back taxes and a fine, and on the Department of Homeland Security producing a border security plan (as in the Senate bill), that could be a real stepping stone to negotiations and possibly even something approximating comprehensive reform.

But if their basic principle is that legalization will only happen after various border security metrics being met — such as E-Verify being fully operational, or proof that 90 percent of border crossers must be being apprehended and 100 percent of the border must be being surveilled — then that’s going to be a very discouraging sign.

In the former scenario, Republicans would pass border security and legalization piecemeal, and the latter would not be directly contingent on the former (perhaps with the exception of something like a DHS plan). Republicans would not be agreeing to citizenship and they would be voting only on piecemeal measures. This could conceivably then lead to negotiations in which Democrats push for an unclogging of existing legal channels to citizenship (such as getting rid of a required return home for those who have been here more than six months, or an increase in green cards). In this scenario, reformers believe, you could get as high as six or seven million gaining a path to citizenship, even as Republicans are not voting for for the dreaded “special pathway” to citizenship.” Dems and reform advocates might accept a deal like this. Conservatives would oppose it as “amnesty,” but it actually is a compromise, in which both sides are making major concessions.

But in the latter, far worse scenario, Republicans would be proposing to take the E-Verify and 90/100 triggers that exist en route to citizenship in the Senate bill and applying them as conditions leading to legalization. The problem with this is that according to reformers, it would essentially leave millions of undocumented immigrants in limbo — still unable to work legally — with no telling whether Republicans would ever agree that those triggers had even been met, particularly if a Republican is elected to the White House.

Frank Sharry, the head of pro-immigration America’s Voice, emails me:

“We all know triggers are going to be part of a final immigration reform bill. But if Republicans put unworkable triggers before initial legal status for undocumented immigrants — by mandating the nationwide E-Verify system has to be operational, or border security has to be 100% — it will put millions of immigrants out of work before they have a chance to get some sort of provisional status. That would be a deal-killer for immigration reform.”

To be sure, we may not know the House Republicans’ full intentions from the principles they roll out, if they are vague on these points. But this is an angle to watch as this unfolds.

Opponents of reform will insist that Republicans demand such triggers in exchange for legalization, precisely because those opponents know it will kill reform. But House Republicans don’t have to go along with that. After all, such an approach would not solve the problem of the 11 million. For all the talk of forthcoming “principles,” what we still don’t know is whether Republicans are really prepared to enter into the compromises necessary to solve that problem. If they allow those who want reform to die to set the parameters of what they are willing to accept, it will be pretty hard to take their motives seriously.

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