Although neither Obama or Clinton will have enough votes to win from the primary voting, most analysts reasonably suggest that if Obama wins Texas and Ohio he will effectively be the presumptive nominee.
More complicated are the scenarios where Clinton wins narrowly in the last three big states of TX, PA, and Ohio. This would leave Obama and Clinton with similar delegate totals and put the race firmly in the hands of the superdelegates as well as a possible change in the elimination of the Floridan and Michigan delegates from the process.
It appears increasingly unlikely that Florida and Michigan delegates will be included given the Obama momentum and also the polling indicating he's far more likely to beat McCain than Clinton. Democratic Party players want to win in 2008 far more than they want a particular candidate, so expect the party to rally around Obama if his March 4 performance is good. If not, expect more indecision as the wild workings of American politics move along.