IN A panel discussion at Harvard University on Saturday, Viet Dinh, who served as assistant attorney general in George W. Bush’s administration and was the chief architect of the USA Patriot Act, was asked whether it was true that Barack Obama’s national security policies were largely a continuation of Mr Bush’s. Yes, he replied, but not because of the choices Mr Obama or any other politician had made. The continuities existed because of a consensus in the law-enforcement, intelligence, and prosecutorial agencies regarding the tools they wanted in order to conduct the war on terror. “Even if Rand Paul becomes president, we won’t see a significant, seismic shift,” Mr Dinh said. On Sunday night, Mr Paul did his best to put the lie to that claim by single-handedly forcing the expiration of parts of the Patriot Act. Mr Paul's filibuster will certainly burnish his credentials with libertarians. But the provisions of the act that have expired are limited. The most important of these regards the ability of the FBI or other agencies to collect and search bulk metadata on electronic communications without obtaining a warrant. Such warrantless searches were presumed legal owing to a ruling by the special federal court (known as the FISA court). But last month a federal appeals court ruled otherwise. And because Mr Paul has forced the Senate to miss the deadline for passing the USA Freedom Act, a new version of the Patriot Act, the authority to carry out such searches has expired.

But as Charlie Savage reports in the New York Times, authorities will still be able to “grandfather in” searches related to investigations opened before June 1st. Because agencies have open-ended investigations into organisations such as al-Qaeda, many warrantless searches can probably continue apace. Judges also rarely object to federal agencies' requests for warrants to conduct specific searches. Meanwhile as soon as Tuesday the Senate will once again grind away at authorising the USA Freedom Act. Mr Paul may try to delay them, but eventually they will succeed.

So Mr Paul's filibuster was essentially an electoral stunt. The deeper issue was not whether Mr Paul himself could succeed in derailing the re-authorisation of the Patriot Act, but whether the libertarian faction in the Republican party (which Mr Paul exemplifies) has become strong enough to cause a real split over national-security issues. This is an important question not only because of what it means for the future direction of Republicans or of conservatism, but because of the implications for lawmaking. Over the past decade it has become increasingly clear that the ideological sorting of America's two-party system—the elimination of liberal Republicans and the weakening of conservative Democrats—has all but paralysed the legislative branch. Ideologically divisive legislation (such as health-care reform for Democrats, Social Security reform for Republicans) can pass only when, as in 2009-10, a single party manages to dominate both houses of Congress and the presidency.