The only thing standing between the United States government and a shutdown is the whim of a group of conservative Republicans. But this time, there's a twist! They're in the Senate.

The compromise budget plan brokered last week by Wisconsin Rep. Paul Ryan and Washington Sen. Patty Murray passed the House by a wide margin, with three-quarters of Republicans voting for it. House Speaker John Boehner was incredulous at the idea that far-right groups might continue to hold a deal hostage. But the measure only needed a majority to pass in Boehner's chamber. In the filibuster-everything Senate, the bar is higher — giving conservatives an excellent chance to make their voices heard.

Last week, Republican Senate leaders announced that they planned to filibuster the measure. (If the bill were an actual budget resolution instead of a policy agreement, Senate rules prohibit any such filibuster. Oh well!) According to Politico, the chamber is getting close to the 60 votes it needs to overcome end the filibuster and proceed to a vote, only one Republican vote shy of the number needed.

So Tea Party groups — incensed at the fee increases included in the deal and the reductions to the sequester — have begun a campaign to lobby those senators. "The GOP controlled House sold us up the river," the TeaParty.net site reads. "Do not continue to stand for this nonsense! Tell them NO NEW TAXES!"

According to Americans for Tax Reform's Grover Norquist, the architect of the no-tax pledge who's now chained to that rock like Prometheus, the fee increases are not a tax. As we explained last week, the increases apply largely to airline tickets. And that, Norquist says, doesn't count. The agreement "structures the TSA ticket fee not as a tax," but as an "offsetting receipt." So: "this fee straddles the line between a tax increase and a user fee without technically crossing into tax hike territory – nevertheless, it should be replaced with spending cuts." This important linguistic distinction, it seems, has so far failed to assuage conservative concerns.

For his part, Ryan, the Republican primarily responsible for the deal, is rising to the defense of the sequestration cuts. On Fox News Sunday, he defended the sequestration reductions — which, in effect, allow more government spending. "In just the next two years, 70 percent of the sequester is intact," he pointed out. "Ninety-two percent of the sequester over the life of the sequester is intact. The Democrats came into this thing saying 'get rid of the entire sequester.'" Which obviously didn't happen.

Newt Gingrich, talking to ABC's This Week on Sunday, even suggested that, while the deal isn't great, quickly passing the budget deal allows Republicans to get back to the important stuff: hammering President Obama on Obamacare.

Easy for him to say. He hasn't been in office for years. For Republican senators — particularly those facing Tea Party primary opponents — they at least have to express their irritation at the deal. Sen. John McCain, who isn't up for reelection but has publicly wavered on the agreement, put it succinctly. "“I’m not OK with it," he said, according to Politico, "but I think it’s better than shutting down the government." That was the prevailing philosophy in the GOP shortly before the shutdown in October, too. Until a conservative senator from Texas turned everything upside down.