In this April 26, 2011, file photo, Rep. Paul Ryan, R-Wis., is silhouetted as he speaks at Gateway Technical College in Kenosha, Wis. (Jeffrey Phelps/AP)

At virtually every campaign stop, GOP vice presidential nominee Paul Ryan hammers President Obama for dreaming up the automatic spending cuts that are set to hit the Pentagon in January.

But as the senior Republican on the House Budget Committee, Ryan himself proposed to cap government spending and enforce those caps with automatic spending cuts that would have hit the Pentagon.

As introduced in 2010, Ryan’s “Roadmap for America’s Future” would have created “a mechanism to automatically slow the growth in faster-spending entitlement programs” by requiring the White House budget office “to make across-the-board spending reductions in both mandatory and discretionary programs” if overall federal spending breached specified limits.

The Defense Department would have been a target for cuts, House Budget Committee aides confirmed Monday, though the impact would have been limited to 1 percent of any agency’s budget.

“It’s fair to say we think we need to have enforcement mechanisms to achieve these reductions,” said one senior budget aide, who spoke only on the condition of anonymity. “But every time Paul Ryan has done it, it’s been part of a plan to actually get spending down to these levels. . . . It was meant as a backstop to force action.”

That enforcement mechanism was not included in the budget resolutions that passed the House in 2011 and earlier this year, the aides said, in part because budget resolutions lack the legal power to create and enforce such caps. Ryan included the mechanism only in the fiscal “roadmaps” he offered as stand-alone legislation beginning in 2008, when House Republicans were in the minority.

Aides to Republican Mitt Romney’s presidential campaign said the proposed cuts in the Ryan budgets can’t be compared with the cuts looming in January, for which they continue to blame Obama.

“Only one person in this race has proposed a plan that would leave our national security at risk, and that’s Barack Obama,” campaign spokesman Brendan Buck said. “Any comparison of the president’s devastating defense cuts that would gut our military and previous House-passed budgets strains credibility.”

Ryan’s use of the mechanism is not particularly surprising. For much of the past three decades, both parties have repeatedly turned to automatic spending cuts designed to slash budgets indiscriminately — a process known as sequestration — as a means to compel action.

In 1985, Republican Sens. Phil Gramm (Tex.) and Warren Rudman (N.H.) joined Democratic Sen. Ernest F. Hollings (S.C.) in drafting one of the earliest sequestration plans, which was designed to hit defense hard to force President Ronald Reagan to the deficit-reduction table.

In 1990, President George H.W. Bush agreed to enforce a deficit-reduction deal by setting separate caps for defense and domestic spending, with each side of the budget liable to get whacked with a sequester if its cap were breached.

Last summer, aides to Obama called on this history during the battle to raise the federal debt limit. Negotiations between Obama and House Speaker John A. Boehner (R-Ohio) over a big deal to reduce borrowing had failed, and Congress was considering naming a special committee to come up with $1.2 trillion in cuts over the next decade in exchange for a rise in the debt ceiling. But how to make the special committee act?

The White House wanted a trigger that would not only automatically cut spending, but also raise taxes. Congressional Republicans rejected that idea out of hand. So, as is recounted in a recent book by Washington Post editor Bob Woodward, then-White House budget director Jacob J. Lew, legislative liaison Rob Nabors, economic adviser Gene Sperling and Bruce Reed, chief of staff to Vice President Biden, “decided to propose using language from the 1985 Gramm-Rudman-Hollings deficit reduction law as the model for the trigger.”

The trigger was approved by bipartisan majorities in the House and Senate, including Ryan. It calls for the $1.2 trillion in cuts to be split equally between defense and non-defense programs starting Jan. 2. In a report issued Friday, the White House said the first round of cuts would take an 8.2 percent bite out of domestic programs and slice 9.4 percent from most security budgets, including the Pentagon’s.

Even before Woodward’s book, “The Price of Politics,” came out this month, Republicans had been blaming Obama for the sequester. Since the book was published, they have made it a central plank in their criticism of the administration.

Late Friday, Senate Republican leaders issued a news release titled, “The Architects Of Sequestration: Obama White House Authored Devastating National Security Cuts It Now Attempts To Disavow,” citing Woodward’s book.

On Saturday in Florida, Ryan pressed the attack: “The only net spending cuts the president seems eager to engage in is to gut national security. It is the primary responsibility of the federal government, and it’s the one he wants to throw overboard first when it comes to taking the pencil out on the budget.”

Jim Horney, a budget expert at the left-leaning Center on Budget and Policy Priorities, dismissed the notion that the sequester was “some new idea of the president.”

“In a way, this is commonplace,” Horney said. “I think it seemed sort of unexceptional at the time this was agreed to last summer. And I certainly don’t remember Republicans making any big fuss about it.”