The former private equity executive who is one of the richest men ever to run for president, is under the gun from the Obama campaign to release more years of tax returns.  Mitt Romney has released his 2010 tax return and estimates for 2011, but does not plan on revealing any more than he has to.  In April, he requested an extension from the Internal Revenue Service to file his 2011 tax forms, it's estimated that his tax liability could be over $3.2 million for last year.