So Paul Ryan is vowing there won’t be any government shutdown this fall. He claims House Republicans will avoid the catastrophic mistake of last year, and will pass a clean continuing resolution funding the government by October 1st, the end of the fiscal year — averting a political disaster heading into the 2014 elections.

But there’s a wild card that may not make this so easy: Obama is expected to roll out his executive action shielding more people from deportations in mid-September, right before government funding runs out. That could prove the political equivalent of rolling a grenade into the House GOP caucus right when GOP leaders are hoping for calm.

Ryan hopes Republicans will line up in orderly fashion behind a “clean CR” that will fund the government through mid-December, averting any shutdown theatrics just before the election. (Remember, the Republican brand tanked badly in the wake of last year’s shutdown insanity.) The question is whether House conservatives will go along.

That’s where Obama’s executive action on deportations comes in. If Obama does something even remotely ambitious — and it’s not clear he will, but it is possible — conservatives will erupt. Ted Cruz will spew charges of lawlessness in all directions as he rampages throughout the Conservative Entertainment Complex. It’s not hard to imagine House conservatives agitating to attach to the CR some mechanism that blocks Obummer’s Amnesty from moving forward. (That’s what happened in 2013, but the focus was Obamacare.)

After all, House Republicans only just got done voting to roll back Obama’s Deferred Action for Childhood Arrivals program — which protects the DREAMers — because conservatives insisted on it as a condition for supporting a bill to address the border crisis. From their perspective, they may now be staring at DACA on Steroids. Given Ted Cruz’s well-established ability to move House Republicans around like pawns, it’s reasonable to speculate that we may see Cruz and other conservatives insist on no CR unless it also does something to block said DACA on Steroids.

It’s my bet House GOP leaders are hoping their lawsuit against the president acts as a valve to release such pressures. They may argue it’s folly for House Republicans to stage another battle around the CR because it could imperil their chances of cleaning up in the midterms — and that they should temporarily confine their war on Obama lawlessness to the GOP lawsuit. But many conservatives think the lawsuit is a stunt — and also see the threatened expansion of DACA as supreme tyranny — so they may not be persuaded to stand down.

House Dems are already needling Republicans on the possibility of a shutdown. DCCC chair Steve Israel said yesterday: “For the sake of our economy, this Republican Congress needs to take shutdowns off the table once and for all.”

For many reasons, the above scenario may not come to pass. Obama may not roll out his executive action on schedule. If he does and conservatives do rebel, House Republicans may have the option of passing something with a lot of Dems, since there may be bipartisan agreement on previously set spending levels. But they may end up getting conservatives very, very angry in the process.

As I’ve detailed here before, the politics of Obama’s executive action are very dicey for Democrats. But they could also prove pretty tricky for Republicans, if it goads them into more dysfunction and infighting.

Interestingly, there’s a slight difference between Senate and House Dems at play here. Senate Dem operatives are worried about Obama’s coming move, because control of the Senate will be decided in places where Obama is already extremely unpopular among white voters. Yet House Dems have been less vocally worried about it. They have more to gain from an outbreak of the sort of House GOP crazy that could be provoked by it.

You can expect House Dems to increasingly call on Republicans to close down the possibility of a shutdown by promptly funding the government when Congress returns — right when talk of Obama’s executive action heats up.

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