Senator Paul said that he agreed with those who say that “Western occupation fans the flames of radical Islam.” That opinion turned many Republicans against his father. Senator Paul’s speech pushed a less interventionist foreign policy in terms designed to appeal to Republicans. The Constitution, after all, dictates that Congress, and not the president alone, should decide when we go to war. With the debt crisis, the United States simply can’t afford all its current and possible future military interventions. Fiscal conservatism, by this line of thinking, means peace.

Just as his father made “Audit the Fed” a popular cause, Senator Paul told me in January, “I think I can do the same with ‘Audit the Pentagon’ ” and fold defense cuts into his party’s conception of fiscal responsibility.

Ron Paul’s son is not his only legacy in Washington. A small group of freshman or second-term representatives he endorsed are admired and scrutinized by his supporters. The most prominent House “Paulite” is the second-termer Justin Amash, of Michigan. There is a new breed of Republicans who “are much more libertarian in their views and have the debt as their primary concern and will fight to protect civil liberties,” Mr. Amash told me last month. “It’s only a matter of time before these individuals work their way up in ranks and become leaders.”

Mr. Amash embraces the libertarian label. “In my district, people have a good idea what it means: limited government, economic freedom, individual liberty,” he says. “They see I’m against wasteful spending and for protection of civil liberties.” Mr. Amash relishes how his libertarianism marks him as a rebel in his own party. He was booted in December from his Budget Committee seat by the Republican House leadership for, he says, voting against leadership-approved budgets that didn’t shrink spending enough for his taste. Then Mr. Amash encouraged a revolt against House Speaker John A. Boehner in his January speaker election. Thomas Massie of Kentucky, a Ron Paul-endorsed freshman, voted for Mr. Amash over Mr. Boehner. Mr. Amash says that the leadership’s anger pleases his constituents; they are “excited about my independence, excited to have a representative fighting for them and not just following the party line on everything.”

While Senator Paul and Mr. Amash alienate some Republicans, libertarian stands against policies like the bailouts and the federal drug war have potential crossover appeal for Democrats and independents. “If we are ever going to win in California again, or Washington, we need someone who is a libertarian Republican,” Senator Paul told me.