Man, after a career of late-night wars, Jay Leno simply will not allow peace in our time. Just a week after David Letterman revealed that he “couldn’t care less about late-night television,†his erstwhile frenemy returned to The Tonight Show, heart on sleeve. The former host/former-former-former host stopped by Jimmy Fallon’s stomping grounds on Wednesday to tell some monologue funnies. Leno mostly jabbed at the usual election-season suspects, but he also did a series of “the economy is so bad†jokes that were … bad. How bad were they? Not great!