If you weren’t paying attention, you might think that there was a liberal Republican named “Ryan Murray” attracting a flood of conservative primary challengers. So swift has been the right’s reaction against the budget deal between House Budget Committee Chairman Paul Ryan and his Democratic Senate counterpart Patty Murray.

“The Ryan-Murray deal is a complete abdication of Washington’s governing responsibility,” thundered Chris McDaniel, the conservative primary challenger facing Mississippi Republican Sen. Thad Cochran. McDaniel followed up with a statement trying to draw out the incumbent: “Mississippi taxpayers deserve to know where Sen. Cochran stands on this disastrous deal.”

Matt Bevin, the conservative challenging Senate Minority Leader Mitch McConnell in Kentucky’s Republican primary next year, took the same tack. “We deserve better and in 2014, we will go to the ballot box and demand better,” he said of Ryan-Murray. Bevin then issued a statement calling on McConnell to oppose the deal.

“McConnell should lead Republicans in demanding a deal that, at a bare minimum, sticks to the existing savings of the sequester," Bevin said. McConnell may oblige, amidst reports that the Senate Republican leader will oppose the deal.

Kentucky’s other Republican senator, Rand Paul, is against Ryan-Murray. So is Marco Rubio, Tom Coburn, Mike Lee, Heritage Action and the Club for Growth. Ted Cruz can’t be too far behind. House conservatives don’t sound too enthusiastic, though the GOP leadership in that chamber has rallied behind the deal.

This is a major test for Paul Ryan, who has emerged as the party’s leader on fiscal policy. Ryan’s bold plans for restructuring Medicare and reducing the country’s debt-to-GDP ratio helped him leapfrog more senior members to become the top Republican on the House Budget Committee. It helped him win a spot on Mitt Romney’s 2012 presidential ticket. His budgets have now passed the full House and won the votes of most Republicans in the Senate.

But Ryan’s record hasn’t always been perfect. He voted for the Medicare prescription-drug benefit, which added to the already underfunded retirement program’s massive unfunded liabilities. He supported the Wall Street bailout. In fact, he won over many wavering Republicans to both causes. Ryan also supported the automakers’ bailout.

The brainy Wisconsin Republican’s conservative credentials survived each government-growing heresy. In many key respects, he has been an important bridge between the House leadership and restive conservatives. But some cracks have appeared in recent years.

Many conservatives have complained about the changes Ryan has made to his budget blueprint. Some have claimed he has watered down his major spending cuts, forcing him to move up the date at which the budget reaches balance in order to calm doubters. When conservative firebrands Justin Amash and Tim Huelskamp were booted off the Budget Committee for voting against the spending plan, critics saw Ryan’s fingerprints on the move. Other conservatives have objected to Ryan’s seeming openness to some version of comprehensive immigration reform, although he has voted against the recent major amnesty bills.

Compared to most of these other heresies, Ryan-Murray is small potatoes. It blows through the next two years’ budget caps, but the $45 billion spending increase is a drop in a $1.012 trillion bucket of federal discretionary spending. It raises airline security fees going to the hated TSA (a point Rand Paul has been quick to make) but that’s the closest thing to a broad-based tax increase; tax rates stay the same.

It’s a bad budget for Republicans. But considering it is a product of cooperation with the liberal Patty Murray, it could certainly be much worse.

But it raises the red flag for good reasons: Ryan-Murray trades certain sequestration spending cuts now for savings in the future. But if the budget caps for 2014 and 2015 are negotiable, why are the ones for a decade from now sacrosanct? If defense industry lobbyists can unwind sequestration for the next two years, why can’t other interest groups do so in the future?

Not only does this debate have the potential to tarnish Ryan’s reputation among fiscal conservatives. It raises questions about his whole strategy for controlling spending. For years, Ryan has been willing to accept government growth over the short term to buy political space for his plans to rein in the beast over the long term.

The early versions of Ryan’s Roadmap phased in spending cuts over many years, including the controversial Medicare reforms, and took decades to balance the budget. But current lawmakers can’t bind future Congresses. Spending cuts spread out over a longer period of time may be less painful, but they are also less likely to happen.

Now Ryan is on record of wanting to get rid of spending cuts he voted for himself while promising savings in the future. Grover Norquist—who was also with him on Medicare Part D—may be on his side, but few other conservatives seem to be buying it.

Ryan has rightly been praised as one of the bravest Republicans in Washington on entitlements. But now conservatives see the Ryan-Murray deal as Wimpy: I will gladly pay you Tuesday for a hamburger today.

W. James Antle III is editor of the Daily Caller News Foundation and author of the new book Devouring Freedom: Can Big Government Ever Be Stopped?

Image: Flickr/Gage Skidmore. CC BY-SA 2.0.