Rudy Giuliani

Grade: C

The frontrunner got far and away the toughest questions — and while he had no disqualifying moments, his overall performance was his weakest to date. Was somewhat plodding and grim — more defensive and less optimistic than usual. Seemed uncomfortable when discussing both the Bible and the Second Amendment. Went after Romney with the line of the night about his rival's "sanctuary mansion" (referencing the illegal immigrants who worked on his yard) — proving yet again that he absorbs opposition research into his brain, and is willing to wield it. But also showed flashes of his mean streak — one of the great dangers he faces as a candidate. Smoothly handled news-of-the-day question from Anderson Cooper about his mayoral billing record controversy, but that one ain't over.

— by Mark Halperin