It is. The project just became a waste of tax payer dollars if the station doesn't accomplish it's goal. To have to construct another one to properly and effectively set up bases on the moon and Mars is exactly the kind of pork-barrel spending that was mentioned that killed NASA in the first place.
It isn't the goal of the ISS to set up bases on Moon or Mars. Its goal is to conduct scientific experiments in an microgravity environment (which admittedly sounds far less sexy, but that's how it is).
Politically, the ISS had also the purpose of tying the Russian space program to the American one after the end of the Cold war.