The key word in Joe Biden’s announcement video is aberrant. If Donald Trump serves only one term, Biden declares, “I believe history will look back on four years of this president and all he embraces as an aberrant moment in time.”

Before Trump, the former vice president implies, a moral consensus reigned. America, he declares, “is an idea”—an idea that “everyone is treated with dignity,” and that “gives hate no safe harbor” and “instills in every person in this country the belief that no matter where you start, there’s nothing you can’t achieve if you work at it.” That, Biden explains, is “what we believe”—or at least we did, before Trump came along.

That’s a fundamentally different message from the one being peddled by Biden’s key competitors, who see Trump not as a historical aberration but as the outcome of a long historical decline. Bernie Sanders and Elizabeth Warren both depict Trump as a manifestation of the class war that the ultrarich have been waging since the Ronald Reagan era; in their telling, this war created the economic insecurity that made working-class whites susceptible to Trump’s racist scapegoating, and Trump is escalating the conflict by handing over the government to corporate and financial interests. Pete Buttigieg, meanwhile, attributes Trump’s rise to America’s long-standing failure to meet the challenges of globalization, a failure that has left Americans susceptible to “the myth that we can stop the clock and turn it back” to an era before automation and outsourcing.

Biden, by contrast, describes Trump not as the consequence of long-festering American ills, but as the antithesis of long-standing American ideals. He starts the video by noting that Charlottesville, Virginia, is the home of Thomas Jefferson, who authored the words All men are created equal. Americans “haven’t always lived up to these ideals,” Biden acknowledges. “But we have never before walked away from them.” Until Trump.

Biden’s distinction—between not “living up to ideals” and “walking away from them”—is meaningless. America “walked away” from the ideals of human equality at its founding, when it enforced slavery, ethnically cleansed Native Americans, and denied women the vote. Since then, America has oscillated between eras such as Reconstruction, from 1865 to 1876, when it moved closer to equality under the law, and eras such as Redemption, when whites reestablished racial supremacy in the years that followed. As Ta-Nehisi Coatesand Adam Serwer have argued, America is experiencing an era like Redemption again today.

In every era, there are different versions of the American idea, some more inclusive and some more exclusive. Discouraging nonwhites from voting—as Trump is doing now—is as deeply American an idea as demanding that they gain access to the ballot. Opposing immigration by people of alien races and faiths is as American as welcoming them.

It’s not surprising that Biden, of all the Democratic contenders, would come closest to a Democratic version of “Make America great again.” He served in the Senate from 1973 until he became vice president in 2009. He has to defend the pre-Trump era. If he described Trump the way Sanders and Warren do—as the product of a decades-long, bipartisan descent into oligarchy—he’d be condemning himself.

Biden’s problem is that while most Democrats like Barack Obama personally, the party has lurched left since he left office, and many of its activists now take a dim view of policies that Democrats once deemed mainstream. Thus, if Biden had entered the presidential race with a standard biographical video describing his many accomplishments in public life (something his website actually offers), he would have immediately prompted a debate about all the positions he once took—on crime, financial deregulation, Anita Hill, and the Iraq War—that Democrats now scorn.

Biden evades that problem in his announcement video, but at a cost. He bathes the past in a warm glow without defending it substantively. And in so doing, he offers a deeply unconvincing historical narrative in which Trump lands upon the American political scene from outer space.

In his announcement speech, Buttigieg warned against romanticizing “a bygone era that was never as great as advertised to begin with.” Although that comment was meant as a dig at Trump, Biden has reason to worry. If his announcement video is a sign of things to come, it could be an effective line against him, too.