I don't know. Nobody ever knows. But a few thoughts:
1. Republicans are making far better use of their network air time. The networks come on at 10:00 EST, and the Republicans have two high-profile speeches. The Democrats inevitably had one speech, and the rest of the time was therefore filled with talking head speculation that did them no good. The Obama speech was fantastic, but much of the rest of the convention was a wasted opportunity. (Bill Clinton's speech was amazing, but not during network time and thus seen by very few people.)
2. Unsurprisingly, the Republicans were way, way more negative than the Democrats. Quite vicious, actually, especially Giuliani who appeared every bit the bully he is. Usually this works better. The Democrats hardly touched McCain, which I thought was a mistake at the time and still do.
3. The Republicans, as Frank notes, are using a familiar cultural polarization strategy. There are, however, times when the GOP strategy of polarization does not work, and this may be one of them. The GOP message consists almost entirelty of mocking Obama and reminding people of McCain's war heroism. They have done very little to position McCain in the center, in a year when he needs a strong margin among independents to overcome the larger number of self-identified Democrats. In a way, they may be making the polar opposite of the mistake the Democrats made.
Frank seems a little spooked. It actually reminds me of 1992 a bit. After Clinton won, Michael Kinsley wrote a column in which he recalled watching the Republican Convention in Houston, every bit as nasty as the 2008 version, and having a sinking feeling that it would work again. Some years this stuff doesn't work. Palin is a great base-mobilizing pick, but partisan polarization is not likely to work for the Republicans this year. Some of McCain's ex-advisors have been warning as much for months. John McCain has turned himself into George W. Bush with a war record.
Related: Why the RNC Isn't Working, by Noam Scheiber