The U.S. citizens deserve complete honesty and transparency from politicians. Their tax returns should be publicly available for public review to fully understand their financial intellect and integrity. If these politicians are taking tax deductions not available to the general public or stretching the bounds of legality, it can and should affect the election.
Presidental canidates should not have to release thier tax returns. They have the right to privacy. But when their taxes become a hotly contended issue in the political race, it certianly would be helpful of them to release their tax forms anyway as a sign of good faith and to show they have nothing to hide.
There is very little to gain from learning about the tax information of presidential hopefuls. If, on the other hand, one is hoping to fight the entire tax system, including the corrupt ways in which government celebrities get less taxation, then the tax records become useful. As it is now, we have a general understanding that they are moderately wealthy. Why do we need to know more than that?
The release of tax returns should not be a requirement for presidential candidates. Instead, it should be expected of candidates to do so. The willingness of candidates to release their tax returns would also be indicative of how they would be as Commander in Chief - whether they would be a transparent president, or a restrictive one.