Bush can win with a minority of the popular vote again even without Nader.
CAN, but probably won't, it seldom happens.
However, given the bias of the electoral college towards low population states, and that these states are Bush's electoral strength, it is no freak of nature that a minority PV president was elected in 2000, and could easily happen again in 2004.
As discussed elsewhere, Bush won with only 47.87% of the PV. If he gained even 0.82% of the total vote, it would offset the combined Gore/Nader 2000 margin in FL and, all else held constant, re-elect him, even though he would trail the Dems in the PV 50.3% to 48.7%
If, as frequently suggested here, FL has become more conservative, he could conceivably pull out a win with even less of the PV.