Ted Cruz turns on his former law professor.

In deflecting an attack on his citizenship, Ted Cruz called Harvard Law School professor Laurence Tribe—who has legitimized inquiries into Cruz’s Canadian birth—“a leftwing judicial activist law professor,” a Hillary Clinton supporter, and Al Gore’s recount lawyer. Some of this is true, and some of it isn’t (Tribe, no leftwing judicial activist, is also trying to undermine the Obama administration’s greenhouse gas regulations). But it’s an interesting attack in that Tribe was once Cruz’s law professor. Notably, Tribe was also Barack Obama’s law professor. But unlike Cruz, Obama hasn’t turned on Tribe by calling him a right-wing climate denier or with any other ad hominem attack.