The answer, I think, is when it comes time to appoint Supreme Court nominees. The nature of our system demands a functioning presidency not just to institute ideologically-tinged reform policies, but just to insure the smooth functioning of the state particularly in foreign affairs. But Supreme Court appointments are another matter. For better or worse, someone needs to exercise the powers of the presidency for the next four years, but that presidency need not necessarily be allowed to ramify decades into the future.
I doubt there is any chance that Bush would actually appoint a Scalia-type ideologue to the court. But say he nominates a solid, though garden-variety, circuit court judge. At this point Senate Democrats might say something like this: "Look, as far as we're concerned you weren't even really elected to the presidency. Yes, we're willing to get-along-and-go-along for four years. But we're not willing to let an historical accident shape the course of the nation's jurisprudence for the next generation." Not with those words exactly, and probably not publicly. But I can't see Senate Democrats seeing the matter much differently. They may demand the appointment of a true moderate and regard themselves as true coequals in the process of appointment.
Of course there are other reasons the process might play out this way. From an institutional standpoint, the Senate has deferred to the president on court appointments over the last generation. The Democrats pioneered the process of applying what we might call "strict scrutiny" to court appointments in the 1980s, and the Republicans took up the mantle with a vengeance under Bill Clinton. For the last eight years Republicans have exercised a de facto veto on truly liberal court appointments, and have in many cases simply refused to bring nominations to the floor at all, preferring to let seats simply go vacant.
Democrats will hardly forget that under a Bush presidency; and controlling 49 or 50 seats under the aggressive leadership of Thomas Daschle will strengthen their hand immeasurably.
What's a dauphin to do? One onlooker proposes that Bush try to trump presidential feebleness with identity politics and appoint a conservative Hispanic jurist to the court. This would play nicely to Bush's inclusive, compassionate conservative image. And Democrats, this observer figures, would simply prove unwilling to deny a seat to the first ever Hispanic appointee, given the growing importance of Hispanic voters and the disproportionate votes they give Democrats.
This is a good point (and good advice as well). But I suspect it's not so simple. Democrats had little difficulty mounting a strong opposition to Clarence Thomas. But of course that was a different matter. Predominantly Catholic Hispanic-Americans are not nearly as stalwart in their support of Democrats as African-Americans are, and Republicans have long believed that Hispanics can be peeled away from the Dems on moral issues--an important point if the rallying cry against such a hypothetical Hispanic nominee is opposition to abortion rights.
Still, I doubt Democrats would roll over so easily. The matter, I suspect, will come down to a strenuous analysis of the nominee's writings and a decision on just how conservative he or she is on the standard litmus test issues.
In any case, back to my main story: Aside from a general atmosphere of illegitimacy or accident that might hang over a Bush presidency, the most tangible effect will likely be in high profile appointments to the courts. Activists with an interest in the court would do well to consider that, and get to work now.