A behind the scenes argument has broken out among Democrats and immigration advocates in the wake of public discussion of a so-called “Plan B” on immigration, in which advocates would press the White House to legalize millions of undocumented immigrants via executive authority if Congress fails to act.

Some have pushed the “Plan B” idea in the media to increase pressure on Republicans to support legislative reform, by getting them to fear Obama would legalize the 11 million himself if they don’t do it on their own terms. But others — including, sources say, the White House — think floating the idea is not only substantively absurd, but is also politically a mistake, because it only takes the pressure off Republicans on immigration by allowing them to slip back into fight-Obama-tyranny-at-all-costs mode.

The “Plan B” idea has generated a lot of attention lately, and for good reason: it’s pretty dramatic stuff. The idea — most recently given a big public push by Marco Rubio — is that if Republicans can’t support immigration reform, then they should fear Obama using his executive authority to legalize the 11 million, just as he did with the DREAMers. Rubio warned fellow Republicans that if they don’t embrace reform, “a year from now we could find ourselves with all 11 million people here legally through an executive order from the president.”

Some immigration advocates have also echoed this idea. Frank Sharry, the head of pro-immigration America’s Voice, recently reacted to Rubio’s comments by claiming that if Republicans punt on reform, “immigration reform advocates are going to do what we did in 2011 and 2012, which is to pressure Obama to use his authority — which is expansive in this area.”

But some inside the immigration reform movement are calling on folks to shut up about this idea. It may be a nonstarter to begin with. In political terms, the thinking is that the conservative backlash to reform has yet to materialize, and House Republicans are feeling pressure to act in a way they haven’t in years. So it’s folly to give GOP base voters who may not be all that worked up about immigration something to get genuinely excited about — a secret, dastardly Obama scheme — which also gives Republican lawmakers a way to claim the opposition can’t be trusted and to slip into anti-Obama battle mode.

“Immigration is not sparking a fiery backlash in the Republican base like it once did, so switching the focus to what Obama might or might not do just doesn’t make sense,” an aide to a House Democrat tells me. “Opposing anything Obama is for still sparks plenty of backlash in the Republican base, even if it is just imagining something he might do.” The aide adds that talk of this nature distracts from the fact that “the focus is 100 percent on legislative strategy.”

I’m told that the White House has expressed to advocates its displeasure with public discussion of the “Plan B” alternative, viewing it as substantive and political folly.

“The White House is very unhappy with any mention of any executive action,” Sharry tells me. “They’re looking for a legislative victory and they have no interest in playing politics. The last thing they want is a distracting conversation about administrative action. They fear Republicans will think they’re up to something when all they’re up to is passing legislation.”

Indeed, the other problem with “Plan B” discussion is it could raise expectations among immigration reform proponents that such mass action is a serious possibility, should reform fail. In fact, the push for reform — and continuing pressure on Republicans to embrace it — remains by far the most viable way forward, and perhaps the only viable one.

“Most in the immigration reform movement are focused on one objective, which is passing legislation this year,” Sharry says. “Legislation is a permanent solution for millions. At best, executive action is a temporary reprieve, and only for some.”