When a presidential nominee announces a running mate, the standard play for the opposition party is to use that running mate to reinforce its existing criticism of the presidential nominee. By the time the veep nominee is selected, the opposition has already defined the presidential nominee, negatively, for a large part of the public. Even swing voters who haven’t fully embraced that negative portrait typically know what it is and have concerns about it.

What’s different this time is that the Republicans haven’t gotten their definition of Harris to stick — in large part because she is such a recent de facto nominee. They haven’t even settled on what criticism they want to lead with: inauthentic flip-flopper, fake black person, lightweight, or extreme left-winger.

If they want to use Walz against Harris, they’re going to have to define two people at once for a lot of voters.