Romney's move today is, in many ways, an acknowledgement by the campaign that not revealing his taxes hurt him in the South Carolina primary.
"We made a mistake for holding off as long as we did," Romney said in a Fox News interview Sunday.
Romney's reluctance damaged his image of leadership, specifically and economic leadership among the broad majority of South Carolina voters who cited the economy as the most important issue, per exit polls.
Gingrich and other candidates attacked Romney feverishly for not disclosing the information. Romney himself struggled to answer questions on why he wouldn't do so, particularly during debates last week, even eliciting boos from the crowd at one point.
Romney's tax records are likely to bring renewed attention to the amount of wealth the former governor has, which could hurt him in a race where the economy and unemployment are top concerns among voters.
Financial disclosures with the Office of Government Ethics showed Romney's net worth to be between $190 million and $250 million. In 2008, his personal wealth made him the richest presidential candidate.
Candidates' wealth "is something that should be considered by people as to what kind of appeal do they have, what kind of relationship do they have with the kind of voters we need to be able to be successful," GOP contender Rick Santorum said today.
But the release of the returns will also help answer questions by the public and press. Romney's standing in polls has plunged in recent weeks. Unfavorable views of the former governor are up by a remarkable 15 percentage points in the past two weeks, with 49 percent of people deeming him unfavorable, the worst of this campaign cycle, according to an ABC News/Washington Post poll released today. Meanwhile, President Obama's favorability is at his best in more than a year. Fifty-three percent view the president favorably versus 43 percent who don't.
Romney's rivals, themselves far wealthier than the average American, were cautious in commenting on the former governor's tax returns, given that most oppose tax increases on any income group.
Santorum said this morning he had not seen Romney's records, but added that his wealth was not news to him.
"We know Mitt Romney is a wealthy man. I'm not going to be critical of someone because they have been successful," he told reporters today after a town hall in Okeechobee, Florida. "We hope we all can be successful and we should have a tax code that people who have that wealth should deploy that wealth to create jobs."
Read Romney's tax returns here:
ABC News' Shushannah Walshe, Emily Friedman and Elizabeth Hartfield contributed to this report.