On Monday, Kamala Harris and the Democratic National Committee started running a new attack ad in Pennsylvania. That’s not noteworthy in itself. Early voting has already started, and the Keystone State has emerged as the election’s most hotly contested battleground. Both sides are hurling plenty of attack ads.

But surprisingly, this ad isn’t directed against Republican nominee Donald Trump. It’s aimed at the Green Party’s Jill Stein, who’s currently polling around 1 percent. The ad shows Stein morphing into Trump while a voice-over warns that “a vote for Stein is a vote for Trump.”

Neither the Barack Obama nor Hillary Clinton campaigns ran attack ads against Stein, even though her campaigns in 2012 and 2016 drew comparable support. Nor did Joe Biden bother attacking Green Party nominee Howie Hawkins in 2020. Harris’s unprecedented move is hard to interpret as anything but a sign of desperation, especially in the context of other developments in the campaign.