The case for Biden’s unique electability rests on his overall popularity as vice president to President Barack Obama and his particular appeal to the blue-collar whites who backed Trump in the 2016 election. Fifty-six percent of Americans said they had a favorable view of the former vice president in a February Gallup survey, including 80 percent of Democrats. A more recent poll, from CNN, shows Biden leading Trump in a hypothetical matchup, 51 percent to 45 percent. That same poll shows Biden losing blue-collar whites by just 13 percent, a better margin than his competitors’ and a huge improvement over Clinton’s 37-point deficit against Trump in 2016.

This would settle the question of Biden’s electability if the election were held today. But if he wins the nomination, he will face a scorched-earth effort against his campaign. And from Clinton’s experience, we know that his personal appeal may not survive the onslaught.

Clinton’s unpopularity at the end of her campaign was a complete reversal from her standing at the start, when she, like Biden, was widely admired by the public. Large majorities held Clinton in high esteem while she was secretary of state — in 2012, 65 percent of Americans said they had a favorable view of her. She was so popular that at the nadir of Obama’s popularity, his aides considered replacing Biden with Clinton on the 2012 ticket. Clinton could even tout a connection with blue-collar whites, who powered her 2008 run for the Democratic nomination.

This, of course, did not last. By November 2016, Clinton was the most unpopular nominee in history, next to Trump. But Trump, at least, was an outsider to American politics. And he used his disruptive presence to draw a clear contrast to Clinton, taking her experience and making it a burden. In fact, you can look at the entire 2016 presidential election as Trump dispatching a series of establishment competitors, turning their records against them and blaming them for the state of the country. Trump has already begun to frame Biden this way, highlighting a foreign corruption scandal that reportedly touches his son, Hunter Biden.

Biden, like Clinton, is extremely vulnerable to Trumpian forms of faux-populist attack. He is a 36-year veteran of Washington who backed the Iraq War, cultivated close ties with banks and credit card companies and played a leading role in shaping the punitive policies that helped produced mass incarceration. As he did with Clinton, Trump can slam him on these issues and sow division among Democratic voters. It’s how he won in 2016 — targeting black voters with Clinton’s past positions to discourage and demobilize them. It worked. For all the focus on blue-collar whites, Clinton also missed Obama’s benchmarks with black voters. Had she reached them — or had she come close — she would be president.