I'm no Romney (or Newt or Obama) fan, but why do voters think they're entitled to see a politician's tax returns? Tax returns have very personal financial information in them and are protected by privacy laws in most contexts. If a politician wants to keep his personal finances private, I frankly don't hold that against him.
It's a desperate move by a desperate dimwit. I could care less about their taxes, any of 'em, any party. It means and proves nothing. If they did not pay them they will get caught.
What the person studies, what kind of grades they make, what kind of papers they write, what extracurricular activities they had, etc. Did they pay their own way through college (working). All of this gives a lot of insight.