Thinking about it a bit more, I think there was a very specific window when we could have changed course from ISS/Shuttle -- 1991 to early 1993.

From the "Space Station Freedom" proposal in 1984 until the demise of the Soviet Union, the Station wasn't going to go away since it was seen as part of Cold War competition. The Russians had space stations, therefore, we would too, by God. Nor was it completely clear in the first few years what an expensive dog it'd be.

During most of Clinton's term, ISS not only was far enough along to have unstoppable domestic political momentum, but it had a key foreign policy link then too -- fostering cooperation with the Russians, and giving Russian engineers something to do other than building ICBMs for every dictator on the planet. Thus plenty of policy wonks and politicians outside the space community who would otherwise have complained about the waste of money, saw a valid goal and didn't really care whether it helped the cause of space exploration or not.

Where there was a window of opportunity was late in Bush Sr.'s term, or when Clinton first came in.

In 1991/1992, the USSR was dead, the deficit was exploding, and NASA's was not in good shape: the Shuttle was only just flying again, the military had divested itself of needing Shuttle services, there hadn't been any spectacular planetary missions for years (I don't think Voyager-Neptune and Magellan count), Hubble was out of focus, and people were still laughing about the $500 billion "Debt Star" Mars mission proposal that had come out of Bush's 1989 SEI. Plus Administrator Truly didn't have a lot of charisma or clout.

If you recall, Congress nearly did kill the Station in 1991 or 1992 (I forget the date, but I do remember listening to Newt Gingrich quoting Star Trek on CSPAN). Had the the Bush Admin *wanted* to kill the Station, especially if they had a creative exploration idea to replace it, it would have been dead 435-0.

Likewise, Clinton nearly decided to kill it in early 1993. There was more contracting momentum by then (and inertia from Congressmen who'd stuck their necks out for it in the earlier debates), but Clinton probably could have made it stuck. In particular, if an Administrator had proposed killing Station and cooperating with the Russians on exploration, that would have succeeded.

Once you combined contracting moment with the foreign policy angle and the fact that success was tied not only to Goldin but Gore (since he had the Russia portfolio), I don't think there was any changing course until we launched it and watched it suffer.