Tonight Democrats got the show they wanted—and President Obama may have gotten the boost he needed.

Appearing in Danville, Kentucky on Thursday night, Vice President Joe Biden gave one of the most aggressive, passionate, and substantive debate performances I can recall. I don’t know how it played with the public as a whole and I don’t imagine it influenced swing voters one way or the other. If I had to bet, the media will spend at least as much discussing Biden’s facial expressions as they will dissecting the exchange over Iran.

But on the domestic policy questions at the heart of this campaign—which also happen to be the issues I know best—Biden made the essential points that President Obama failed to convey last week. And Biden did so in a way sure to fire up liberals, whose disappointment over last week’s performance appears to have been a significant factor in Obama’s sliding poll numbers.