While it stands to reason to examine the tax returns of senators and representatives, the Constitution doesn't attach the "high crimes and misdemeanors" restriction to any of those posts. Just to the presidency.
It also says:
"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated"
And that includes presidential candidates. It has been a tradition for candidates to release tax records. Its not a law. Its also a tradition for candidates to release college and university records. We know that Obama has broken that tradition. Why don't you and your ilk apply the same standard to Obama and assume that his college records contain evidence of high crimes and misdemeanors?