Obama: Welcome to the 'Burgh, Mitt. What you hiding?

When Republican Mitt Romney arrives in Pittsburgh Tuesday, he’ll be greeted by a 30-second television attack ad from President Obama’s re-election campaign that rips him for refusing to release more than two years of his tax returns.

“Makes You Wonder” asks what Romney is hiding. Obama, and many leading Republicans, including the governor of Alabama, have been urging Romney to release more tax information. Based on what is known, the former private-equity tycoon has used tax havens and other offshore bank accounts, and pays a far lower effective tax rate than millions of the middle class.

No law requires presidential candidates to release tax returns, which are private, but disclosure has been an element of national politics since at least 1952, when GOP vice presidential nominee Richard M. Nixon challenged his opponent to do so. Nixon was under fire for taking gifts from supporters; he made the famous “Checkers” speech about his finances but, despite the gambit, did not release his returns then. In 1968, Nixon did release the returns. (h/t Wall Street Journal).