MEGAN McARDLE: Biden and Harris are playing a Trumpian game on vaccine safety

Democrats have a good argument that they’re the only party in this election actually looking out for the good of the country, rather than narrow self-interest. One need only consider the way the two presidential candidates responded to a question during last week’s debate about the likelihood that it could take some time to get a definitive vote count:

“Will you urge your supporters to stay calm during this extended period, not to engage in any civil unrest? And will you pledge tonight that you will not declare victory until the election has been independently certified?”

Joe Biden answered: “Once the winner is declared after all the ballots are counted, all the votes are counted, that’ll be the end of it… . If it’s not me, I’ll support the outcome.” President Donald Trump steadfastly refused to make a similar declaration.

So Democrats have a good claim that they are the real party of “America First.” Unfortunately, they undercut it every time they suggest there could be something wrong with any good vaccine news we hear before the election.

Biden slyly implied as much during the debate: “In terms of the whole notion of a vaccine,” he said, addressing viewers at home, “we’re for a vaccine, but I don’t trust (Trump) at all. … What we trust is a scientist.”

This was positively restrained compared with Democratic vice-presidential nominee Kamala Harris (Calif.), who told CNN recently that she’d hesitate to take any vaccine approved before the election, after suggesting that government experts overseeing the approval process would be “muzzled … suppressed … sidelined. Because he’s looking at an election coming up in less than 60 days, and he’s grasping for whatever he can.”

But there are some things no decent person or party can do for political advantage. One is to cast doubt on a potentially lifesaving vaccine during a pandemic.

The defenders of Biden and Harris would argue that they didn’t actually say you shouldn’t take any vaccine that was overseen by the Trump administration. But that defense is positively, well, Trumpian. As is the behavior: clearly imply something unconscionable, but don’t quite say it outright, so that you can distract your opponents with endless quibbles about what, exactly, you said, rather than having to either own or repudiate your words.

Clearly, the perception of political influence is a problem, especially with the Centers for Disease Control and Prevention guidance, but it has also been a problem for the Food and Drug Administration, where accusations swirled around its approvals of hydroxychloroquine and convalescent plasma. But Trump did not get the CDC to claim that COVID-19 is just a bad cold. And he won’t get the FDA to approve a useless or dangerous vaccine.

Trump’s awful behavior certainly stokes such fears, and Biden and Harris are only voicing worries the Democratic base already had — a declining fraction of Americans say they’ll take a vaccine immediately, thanks largely to concerns about the approval process.

But that’s precisely why politicians such as Biden and Harris must reassure them. If they don’t, the fear will linger long after the election.

If Trump loses, Biden and Harris will, of course, be eager to assure people that any available vaccine is A-OK! Marvelously effective! But by then it will be too late: The seeds of doubt they planted will be in full flower. Such distrust could prove deadly, not just for individuals who will get sick as a result of it, but also for a new administration trying to guide the United States into a post-pandemic world.

Follow Megan McArdle on Twitter, @asymmetricinfo.