Politico has a good article on the DEM fight for President and the potential of a tie.
The Democratic race has entered its World War I phase, a bloody fight between two adversaries making only the most incremental of gains. And there is no reason to think either side will emerge from the trenches anytime soon. There are 10 scheduled contests left, but thanks to proportional allocation, not enough pledged delegates to be had for either Barack Obama or Hillary Rodham Clinton to clinch the nomination. And, because of increasingly firm demographic voting trends, it appears to be a foregone conclusion who will capture most of the remaining states. So on June 3, when South Dakota and Montana end the current voting calendar, the contours of the race aren't likely to be much different from what they are today. That means 2 1/2 months of conference calls, attacks, counterattacks and millions of dollars spent, all to move the political needle just a few inches.