My guess is that if Clinton steps down (as part of a plea agreement--so that Gore doesn't have to pardon him), Gore will win in 2000. Remember that President Gore only has to do very slightly better than candidate Gore did in OTL in order to win. In fact, just not returning Elian Gonzales to Cuba will probably be enough for him to carry FL and therefore the Electoral College. Even apart from that, simply being the incumbent president at a time of peace and prosperity will probably be enough. (Incumbency--even after a tougher primary challenge than Gore is likely to get, and in worse economic times, and with the burden of the Nixon pardon--was almost enough to elect Ford in 1976...)
Of course if Gore takes office before January 20, 1999 and wins in 2000, he will not be eligible for re-election in 2004.