In the early-morning hours of Sunday, a scuffle broke out between Fox News correspondent Jesse Watters and Ryan Grim, the Huffington Post’s Washington bureau chief. The fight — unusual among a tuxedo-clad crowd more used to venting their differences with Twitter snarks — briefly caused ripples in the party, where political staffers and journalists were grooving to tunes spun by DJ Biz Markie and noshing on mini servings of chili cheese fries.