During “those eight years, before Obama came along,” Giuliani said, “we didn’t have any successful radical Islamic terrorist attack in the United States — they all started when Clinton and Obama got into office.”

Warming up the crowd for Donald Trump on Monday in Youngstown, Ohio, former mayor of New York Rudy Giuliani offered a glimpse into the alternate reality he has now signed on to by describing the presidency of George W. Bush as a time of undisturbed peace and security for Americans.

Giuliani, NYC mayor during 9/11, says there were no "successful radical Islamic terror attack" in 8 yrs before Obama pic.twitter.com/0A6qQH9clR

Given that Giuliani’s entire post-mayoral career has been based on the fact that he was the mayor of New York City when the World Trade Center was destroyed on September 11, 2001 — eight months into Bush’s first term, and more than seven years before Obama succeeded him — it was a bizarre mistake for him to make.

What made the lapse even harder to explain was that it came just seconds after Giuliani had mentioned the attack in 2001 and praised Trump’s running mate, Mike Pence, for visiting the site of the collapsed towers with him that year.

But as Jeet Heer, a senior editor at the New Republic, observes, Giuliani didn’t forget about the attacks in 2001, he just doesn’t think they should count.

“According to Republicans like Giuliani,” Heer explains, “Bush can never be held accountable for 9/11, while everything that happens under Obama’s watch, from ISIS to Syrian civil war, is the president’s responsibility. This sort of partisan logic might make sense to die-hard Republicans, but it comes across as unhinged to everyone else.”

Giuliani has been pursuing this odd case for quite some time. In an interview with ABC News on January 8, 2010, the former mayor told George Stephanopoulos, “We had no domestic attacks under Bush.”

For his part, Bush himself repeatedly argued that his administration “kept America safe” in the years after 9/11, in part by bringing “freedom” to millions of Afghans and Iraqis.

The former mayor’s selective memory about 9/11 is particularly apt, given that the candidate he is now supporting, Donald Trump, falsely claims to remember watching news footage that day (which does not exist) showing “thousands and thousands” of American Muslims in New Jersey cheering as the towers fell.

Adding a layer of irony to the fact that Giuliani made his remarks on Monday in support of Trump is the fact that Trump himself stunned the Republican establishment in February by mocking the idea that Bush had kept Americans safe, since “the World Trade Center, during his time in office, came down.”

The worldview that everything that’s gone wrong in the United States in recent years is Obama’s fault has deep roots in the Trump campaign. Just two weeks ago, Trump’s national spokesperson, Katrina Pierson, nonsensically claimed that President Obama was responsible for the death of an American soldier who was killed in Iraq in 2004, five years before he took office. On Saturday, Pierson told CNN that Obama had also started the war in Afghanistan.