Which fan base do you think is more Republican? Giants or Jets? 49ers or Raiders? Yankees or Mets?
Giants
Raiders
Yankees
I would actually guess that the Jets and Mets are more likely to be Republican. If you take a look at the geographic distribution of Giants vs. Jets fans and Yankees vs. Mets fans (and the two splits are very similar), the Jets/Mets have more of a base in Long Island, whereas the Giants/Yankees dominate Manhattan, Westchester and north. (New Jersey, where I grew up, is more of a mix, with the Giants and Yankees dominating but not by that much). And LI seems to me more blue-collar and swingy than Manhattan/Westchester, which is solid liberal even in the rich parts.
Also, for Giants vs. Jets another thing to keep in mind is that in addition to geography age is a factor. The really old folks are Giants fans, because that's all there was. A lot of the younger Boomers, a really conservative demographic, came of age when the Giants were horrible and the Jets had won more recently (SB III), so they're more likely to be Jets fans. But then you have my generation, which grew up with the Bill Parcells glory years (or just past them) and became Giants fans- and we're one of the more liberal cohorts.
Okay, maybe I'm assuming that Giants fans are more liberal because I'm a liberal and a Giants fan and I'm just projecting. But I really think the analysis holds.
I think you're definitely right that the Raiders have more conservative fans, though.
...
I agree with the general sentiment that sports fans, in general, are going to be more conservative than the population at large, for many reasons. Even hockey, which might be popular in the colder "blue" cities, because its fanbase is also much whiter than that of most sports. And college sports fans are way, way, more conservative than pro sports fans, because of the urban/rural divide, appeals to "tradition", and historic base in the South. The average football fan is definitely conservative, but the NFL is almost even, and found almost everywhere, whereas college football is probably about as Republican as golf, and as ignored in the Northeast as NASCAR.