From today's NYT: "As the Florida Marlins surged in the playoffs, fair-weather fans began snapping up tickets and basking in the sunny promise of a World Series championship." The article also includes a graph showing how attendance at Marlins games was abysmal for most of the season until it became plain that they were in contention for the playoffs.
The problem with seeing all this in the New York Times is that endlessly-self-congratulatory Yankees fans can imagine that they are not fair-weather fans because, gosh, they've been following the Yankees since they were kids. But, guess what, the Yankees have had at least intermittently fair-weather since their parents were kids? The last time the Yankees had a season as bad as Florida's 1998 season was 1908. We can only imagine what kind of loyalty Yankees fans would show if George Steinbrenner had some kind of strange ascetic conversion and sold off all the teams good players and replaced them with overmatched rookies from the team's minor league system, which is what happened to the Marlins in 1998 and which vitiated the burgeoning loyalty of its fan base.
I just looked it up, and the Yankees attendance fell off by a third when they went from 85-76 in 1988 to 76-86 in 1992 (2.6 million vs. 1.7 million).