A now-familiar theme is playing out today in Washington. A grand bargain worked out between leaders from both parties gains significant steam and heads for passage, only to careen off the rails at the last minute when far-right members of the House of Representatives lay down on the tracks. So why does this keep happening?

On Saturday morning, the Senate passed a bill that would extend a payroll tax cut and federal unemployment insurance for two more months, while preventing doctors from losing over a quarter of their annual Medicare payments. It also contained a Republican provision to force President Obama to issue a decision on the Keystone XL pipeline within sixty days.

Democrats wanted more—they originally asked for a year-long payroll tax cut, at a lower rate, and paid for with a surtax on incomes over $1 million. And even if the Keystone provision could kill the project, as the Obama administration is now signaling, Democrats didn’t want that in there, either.

But the deal was made, and eighty-nine Senators–including thirty-nine Republicans and Tea Party stalwarts like Senator Marco Rubio–voted for it. Senate Majority Leader Mitch McConnell was seen high-fiving fellow Republicans after the vote, and House Speaker John Boehner, who had been a party to the compromise bill all the way, called the bill a “good deal” and a “victory” on Saturday morning. The payroll tax cut would save families an average of $1,000 next year, and every dollar spent on unemployment insurance increases the annual GDP by $1.61.

Later that day, Boehner took it to his members, urging them on a conference call to pass it. It wasn’t pretty.

“I never heard words like ‘sucks’ and ‘crap’ in a GOP Conference,” one member told Fox News’s Chad Pergram afterwards. “Everyone sounded angry.”

A leader of the Tea Party in the House, Florida Representative Allen West (seen earlier in the week comparing Democrats to Joseph Goebbels), blasted the deal as “liberal Democrat incrementalism.” Twenty-four hours and 180 degrees later, Boehner was on Meet the Press saying the bill wouldn’t pass the House.

Already, four Republican Senators (each of them up for re-election in 2012, I would note) have blasted House Republicans for not passing the bill. But the rank-and-file there—which contains sixty members elected in the Tea Party wave of 2010—isn’t listening. They will probably defeat the Senate bill late today.

There have been a series of nonsensical arguments put forth by GOP leadership in the House as to why they oppose this deal. Some say the two-month extension creates “uncertainty,” but Republicans wouldn’t sign off on a clean year-long extension in the first place, which is why the deal is for two months. And the charges of “liberal Democrat incrementalism” would be news to the thirty-nine Republicans in the Senate who voted for it—and who succeeded in junking the millionaires surtax and adding the Keystone provision.

So really, why the vehement opposition? A compelling argument lies in a recent op-ed for the Guardian by Jonathan Freedland, titled “How Fox News is helping Barack Obama’s re-election bid.” He is speaking about the Republican nominating process, but I think the central argument applies to these rebellious House members as well:

Fox, serving up constant outrage and fury, favours bluster over policy coherence. Its ideal contributor is a motormouth not a wonk, someone who makes good TV rather than good policy. Little wonder it fell for Cain and is swooning now for Gingrich—one of whom has never held elected office while the other messed up when he did, but who can talk and talk—while it has little interest in Romney and even less in Jon Huntsman, even though both have impressive records as state governors. The self-described conservative journalist Andrew Sullivan says that the dominant public figures on the right are no longer serving politicians, but “provocative, polarising media stars” who serve up enough controversy and conflict to keep the ratings high. “In that atmosphere, you need talk-show hosts as president, not governors or legislators….

So far, so bad for the Republicans. Why should anyone else care? Because the Fox insistence on unbending ideological correctness turns every compromise—a necessary staple of governance—into an act of treachery. The Republican refusal, cheered on by a Fox News chorus, to raise the US debt ceiling this summer, thereby prompting the downgrading of America’s credit rating, is only the most vivid example. The larger pattern is one of stubborn, forced gridlock, paralysing the republic even now, at a moment of global economic crisis.

Notably, many of the House Republicans up in arms right now are frequent Fox News guests. Allen West, who has appeared on the network dozens and dozens of times, is the prototypical example of “a motormouth, not a wonk.” (See here, here, here and here just for starters). Representative Jim Jordan, leader of the powerful, ultra-conservative Republican Study Conference in the House, made his motivations clear recently, when talking about a House version of this same bill: “The fact that the president doesn’t like it makes me like it even more,” he said.

And, yes—Fox News has been similarly combative and polarizing on the payroll tax cut in recent weeks, sounding, like Jordan, much more eager to hand President Obama a defeat on payroll tax cuts than anything else.

For example, Fox & Friends co-host Gretchen Carlson was interviewing White House Press Secretary Jay Carney earlier this month and blasted the idea of a payroll tax cut. “We’ve already had that,” she said, and “I see dismal [job] numbers.” Lest viewers think the situation might be more complex than that, don’t worry—Carlson said she spoke to “tons” of economists. (Media Matters has a good roundup of Fox News attacking the payroll tax cut over the past several weeks here).

The situation is in full meltdown mode for the GOP now, of course—thirty-nine Republican Senators were just embarrassed and made to look insufficiently strident by their House colleagues. Boehner must now try to get the House to pass the Senate bill with nearly all of the Democratic votes and as many Republican moderates as he can wrangle, which would solve the immediate problem but carries with it the not-insignificant chance the rank and file would rebel against him and possibly even take his speakership. If he chooses not to go that road, as it appears he won’t, the “Tea Party Tax Hike” will likely take effect on January 1—and the White House won’t let voters forget it.

Much belatedly, and with no recognition of their prior opposition, Fox News is now calling for the passage of the payroll tax cuts. (Rogers Ailes is no dummy). But the virulent forces unleashed by the network can’t simply be turned off. Right after he was elected, Allen West pledged to work until “this liberal, progressive, socialist agenda, this left-wing, vile, vicious, despicable machine that’s out there is soundly brought to its knees.” He’s not going to just say “never mind.”