Democrats continue to pressure GOP presidential candidate Mitt Romney into releasing more of his tax returns.

So far, Romney has resisted releasing more than his full return from 2010 and an estimated return from 2011. He said he’s done what is legally required.

Mitt Romney/AP File Photo

Twenty-two U.S. mayors, including Philadelphia Mayor Michael Nutter, a Democrat, have signed and released a letter to Romney urging him to release more information.

“President Obama has released 12 years of tax returns, John Kerry released 20 years’ worth and Bob Dole released nearly 30 years,” the mayors said in the letter.

“Even Richard Nixon released more years of tax returns than you,” they said.

“Remember when you auditioned to be John McCain’s vice presidential pick? You gladly handed over 23 years of tax returns. Now, as you audition for the American people, you think only one full year is good enough. It isn’t,” they said.

Some Republicans also have urged him to disclose more to end the issue.

What do you think? Should Romney release more of his tax returns?

– John Guerriero