This is a bit of a stereotype. All the Nats need to do is have one playoff run and you will see the passion of the fans.
The Skins already showed by selling out when they were losers that there's enough of a local fanbase when there's a hint of hope. The fans have showed up for the Nats plenty, but when the regional population about triples in a generation with imports from elsewhere who can't make the same bank back home, it's not going to look monolithic in the stands as it may elsewhere.
Mostly thoug for the playoff runs, the fans have represented, though like the Caps, it hasn't been easy. Was at the 18-inning game, and the amount of people who stayed even as the weather turned -- and was nearly all Nats fans -- was as good as it gets.