In October 2010, one month before a historic wave of Tea Party Republicans swept into power, Washington's conservative establishment banded together to spread an urgent message to any would-be budget cutters on or near Capitol Hill: Hands off the military, kids.

The $80 million Heritage Foundation, the $30 million American Enterprise Institute (AEI), and the $2 million Foreign Policy Initiative—neoconservative titan William Kristol's latest outfit (partial motto: "strategic overreach is not the problem and retrenchment is not the solution")—combined forces that month to produce a document titled "Defending Defense: Setting the Record Straight on U.S. Military Spending Requirements." In it, the establishmentarians lamented "two decades of underfunding the military," celebrated the "bipartisan consensus" about "America's global leadership role," and cautioned deficit hawks that "defense is not the source of the federal government's fiscal woes."

Kristol, AEI President Arthur Brooks, and Heritage President Ed Feulner underlined their message in a Wall Street Journal essay, arguing that "anyone seeking to restore our fiscal health should look at entitlements first, not across-the-board cuts aimed at our men and women in uniform." The lead editorial in the next issue of Kristol's Weekly Standard warned incoming House Republicans to avoid a "myopic focus on government spending." James Jay Carafano, vice president for foreign and defense policy studies at Heritage, predicted in The Daily Caller that the Tea Party's hawkish faction would win out over its foreign policy "libertarians." Referring to Rep. Ron Paul (R-Texas), a two-time candidate for the Republican presidential nomination, and Rep. Barney Frank (D-Mass.), a longtime critic of bloated military budgets, Carafano explained that "the Barney Frank–Ron Paul project that calls for slashing Pentagon spending is close to a Looney-Tune alliance."

You can see why the old guard was getting defensive about defense. Many of the new breed—including Sens. Mike Lee (Utah), Pat Toomey (Pa.), Marco Rubio (Fla.), and Rand Paul (Ky.), Ron Paul's son—came to prominence only after vanquishing establishment-favored Republican moderates in primary elections, often in campaigns that focused explicitly on cutting, as opposed to limiting the growth of, government spending. And some—especially Paul and Rep. Justin Amash (Mich.)—bucked recent conservative orthodoxy by talking openly of cutting military spending, restraining the executive branch's ability to prosecute war, restoring the civil liberties lost since 9/11, and rethinking America's vast commitments abroad. "The Tea Party," Rand Paul claimed in his post-election book, The Tea Party Goes to Washington, "is now a threat to the old Republican guard precisely because its stated principles prevent it from being brought into the neoconservative fold."

Neocons initially treated Rand Paul like a double agent. "On foreign policy, GWOT [Global War on Terror], Gitmo, Afghanistan, Rand Paul is NOT one of us," former Dick Cheney aide Cesar Conda wrote in a March 2010 email message to many people affiliated with the Foreign Policy Initiative, including directors William Kristol, Robert Kagan, and Dan Senor. "It is our hope that you can help us get the word out about Rand Paul's troubling and dangerous views on foreign policy."

But since then Paul has engaged in a remarkably successful campaign to woo Republican hawks just enough to earn his comparatively radical foreign policy a respectful hearing from people who wouldn't give his father the time of day. As a result, libertarian ideas about reducing America's vast global footprint are no longer on the margins of the GOP debate: they're being championed by a respected senator who is considered a credible candidate for the party's next presidential nominee.

At the 2012 Republican National Convention, where his father was not invited to speak, Paul was offered a prime-time podium slot, during which he insisted that "not every dollar spent on the military is necessary or well-spent," and that "we must never—never—trade our liberty for any fleeting promise of security." Such words would have been unthinkable at a Republican convention as recently as 2008.

An old foe, Senate Minority Leader Mitch McConnell (R-Ky.), became one of Paul's best Senate pals, hiring former Ron Paul campaign chairman Jesse Benton to run his re-election campaign. Paul partnered with uber-hawk Lindsey Graham (R-S.C.) on entitlement reform and has even joined old warhorse John McCain (R-Ariz.) on the Senate Foreign Relations Committee.

Even though Paul endorsed Mitt Romney for president in June 2012 (thus earning a fair amount of enmity from his father's supporters), he did not hesitate to criticize the GOP standard bearer over military affairs. "Defense and war spending has grown 137 percent since 2001," he wrote at CNN.com in October, responding to Romney's biggest foreign policy speech of the campaign. "That kind of growth is not sustainable."

Since Romney lost and Ron Paul retired from Congress, Sen. Paul has been running for president in all but name. When Breitbart News asked him a hypothetical question in January about what "President Paul" might do, he interrupted and said, "I like the ring of that." When I participated in a phone conference with him in February, he declared: "I do want to be part of the national debate and the international debate."

That last project may be the most intriguing. Ron Paul vaulted to prominence and jump-started a political movement by lobbing rhetorical bombs against war from the foreign policy margins, then watching as the bipartisan consensus recoiled in horror and a new coalition of fed-up anti-war voters came out of the woodwork. The single most frequent question longtime Republicans would ask about Dr. No was one that showed they fundamentally did not understand either him or his appeal: Couldn't he, you know, just tone down the blowback rhetoric a bit?

That's where Rand Paul comes in, to the occasional chagrin of Ron Paul's fan base. While Sen. Paul has fought to de-authorize the War on Terror and explicitly delink sanctions from war as a response to Iran's nuclear ambitions, he also voted yes on the sanctions. While he repeated Ron Paul's position about ending foreign aid to Israel, he has prioritized ending foreign aid and military sales to Israel's enemies first and even declared in January that an attack on the Jewish state should be treated as an attack on the United States. In a major foreign policy address in February, he made clear he was not a carbon copy of his father. "There are definite differences," he declared.

Paul's speech, in which he advocated a George Kennan?style "containment" to cope with "radical Islam" and stressed the constitutional separation of war powers between Congress and the president, was not the kind of anti-imperialist critique that audiences have come to expect from Ron Paul. He framed it as an attempt to seek a third way between "isolationism" and constant intervention. But his vision of a smaller overseas commitment and greater skepticism about American omniscience, however vague, represents one of the most radical foreign policy rethinks the Senate has seen in decades.

Just as significant as Paul's words was where they were spoken: the very Heritage Foundation that was firing warning shots across the Tea Party's bow 27 months before, now headed by Paul's good friend and former Senate ally, Jim DeMint. Even the Foreign Policy Initiative's Robert Kagan, while critical of Paul's speech, declared that "people who care about U.S. foreign policy should be grateful for Rand Paul."

As this issue was going to the printer, House Republicans surprised many observers by vowing to let automatic spending cuts, including an estimated $55 billion hit to the military budget, take place as scheduled on March 1. The establishment foreign policy consensus may be changing at long last, thanks in part to the most anti-establishment member of the 2010 congressional class.