Mitt Romney has steadfastly refused to release more than two years of tax returns despite mounting pressure from the Obama campaign and even some fellow Republicans, who are beginning to grumble both publicly and privately that Romney should disclose more details about his income and put the nagging issue behind him.

Romney says that two years of tax returns are sufficient, and that he's fully complied with the law by revealing his full 2010 return and an estimate of 2011 tax information (he plans to make the full return public once it's finalized).

That stance is mostly consistent with Romney's position during his 2002 campaign for Massachusetts governor.

Romney's Democratic rival that year, Shannon O'Brien, released her tax information and called on Romney to do the same.

Romney repeatedly declined.

"People who run for public office are exposed to extraordinary scrutiny and that's as it should be, but there are some things that are not required for release, that are private, and I think my own income taxes, and my net worth and so forth are things I'd like to keep between myself and my family," Romney said in May 2002, according to the Boston Herald.

His longtime strategist Eric Fehrnstrom cited the family's "privacy" and noted that state law did not require candidates to provide anything more than a financial disclosure form filed with the state Ethics Commission.

But Romney has also called for greater tax transparency in the past when it served his political purposes.

In the 2002 race, Romney sought to turn Enron into a campaign issue when it was revealed that O'Brien's husband, Emmett Hayes, had lobbying ties to the scandalized energy and commodities firm.

Hayes had filed his taxes separately from O'Brien - and Fehrnstrom, then Romney's deputy campaign manager, demanded that O'Brien come clean about her husband's financial ties to Enron.