With the terror of last week's Boston Marathon bombing still seeping into the American psyche, how ironic it is that President Obama traveled this week to Dallas for the opening of the George W. Bush Library. Mr. Obama has built the politics of his presidency—its foreign policy and its economic policy—around the assertion that he is the Un-Bush.

Now, in the grimmest way possible, he is Bush, another American president who must come to grips with the aftermath of a mortal act of Islamic terror on U.S. soil, televised to the whole world. Whether the Boston killers were put in motion by Islamist handlers or sprung from Tamerlan Tsarnaev's fundamentalist reveries, jihad has come home to the Obama presidency.

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Columnist Dan Henninger on President Bush's terror vindication. Photos: Associated Press

Mr. Obama is the luckier of the two presidents. His bombing happened at the start of his second term, after he'd already passed the Affordable Care Act and Dodd-Frank. Not so Mr. Bush. The Sept. 11, 2001 destruction of the World Trade Center towers, the driving of a passenger airliner into the Pentagon, and the crashing of another airliner in Pennsylvania changed the course of Mr. Bush's young presidency.

Mr. Obama's tour through this era of Islamic terror has been lucky in one other way: George Bush immediately used his political capital—and paid a heavy price—to pass the Patriot Act. What happened next in Washington wasn't entirely expected.

A consensus had formed back then that 9/11 "changed everything." Some of the "changed everything" mood returned in recent days, with American flags flying around Boston and chants of "U.S.A."

One of the things that was thought to have changed the first time was politics. From 9/11 forward, the war on terror was going to be bipartisan. Surely most Americans in 2001 wanted political solidarity in the antiterror effort to last. It didn't. It collapsed, and in a very short time.

The Bush administration announced the Patriot Act in October 2001. Congress passed it within days. But the assault from the left on its provisions began almost immediately, and the Bush antiterror effort became a policy war zone that lasted years. By 2006, some Democrats—angry at the Patriot Act, the Iraq war and the "torture" of al Qaeda operatives under CIA interrogation—were exploring Mr. Bush's impeachment.

On Boston Commons the morning after the capture of Dzhokhar Tsarnaev. AFP/Getty Images

Bear in mind that the primary questions being asked now are what, if anything, the FBI knew about Tamerlan Tsarnaev's descent into Islamic extremism, and what, if anything, they did about it. The Patriot Act created the means to answer such questions. Its primary weapon to prevent terror was the wiretap, a surveillance tool virtually everyone in law enforcement says is the best way to catch criminals. Two sections of the Patriot Act—the "lone wolf" provision and "roving wiretaps" (both requiring authorization by a special court)—were created precisely to identify and monitor an individual like Tamerlan Tsarnaev before he detonates a bomb in a crowded public place.

Who can forget how the structures created to prevent more terror on U.S. soil turned into a pitched battle that consumed Washington policy makers for nearly a decade after 9/11? Accusations poured forth about "illegal domestic eavesdropping" and a "domestic spying program," which violated "our values."

It was all politicized hothouse hooey. No such thing happened. When its turn came, the Obama administration used the Patriot Act—its title now grimly appropriate—and defended it in court. In 2011, the Obama administration embraced reauthorization of the Patriot Act, which Harry Reid years earlier promised to kill. On at least this one important issue, the Un-Bush president has been very much his reviled predecessor's mirror image.

But let's, so to speak, cut to the chase. In contrast to the Bush era fight over how many judges had to approve surveillance of terrorism suspects, we had the transfixing spectacle last week of Bostonians okay with having their city transformed into a state of virtual martial law after the bombs went off.

The citizens of Boston and its suburbs allowed massively armed SWAT teams to enter their homes, order residents out and eventually find the bullet-riddled Dzhokhar Tsarnaev lying half-dead in a boat. When it was over, people lined the streets to cheer the police army. You'd need more than a roving wiretap to find a peep of objection from the old Bush critics.

Who's to quibble? Some are now asking whether the protections after 9/11 have waned in the past 12 years. After these events, a responsible Congress should want to find out.

But let us posit an unimpeachable fact: Whatever their eventual opinion of "Bush-Cheney," Bostonians and Americans generally would have happily signed off on a warrantless wiretap of the Tsarnaevs' phones before the deaths and mutilations of April 15, 2013. The long fight over the Bush domestic antiterror effort was a case study in partisan extremism run amok in Washington, even as a silent majority of Americans across the political spectrum wanted such protections.

If at last we have consensus on the antiterror war, so be it.

Write to henninger@wsj.com