I just spoke with a Professor of Education at Rutgers who had a Bernie Sanders bumper sticker and a Mass. license on his car. He couldn't vote because he just was moving to NJ but he really was undecided. His comments were very interesting. He sees Clinton as OK, but thinks that she would unite the Republicans against her. He sees Obama as inspiring but thinks his campaign may be premature, because of his age, not ethnicity, and eight years from now might be a better time to run. He also said that his wife in Massachusetts is in the same situation, still not sure whom she will vote for, but she will vote. The important thing, he said, was to beat the Republicans. When I said, like Bernie Sanders, I was for socialism, he said he was too.
If this is anything, it means that on primary day, a sophisticated progressive voter is still very undecided. It may mean that many voters will make their decision when they enter the polling booth.