Fiery debate tops bizarre campaign day in S. Carolina

The former Massachusetts governor had other challenges in a state where unemployment approaches 10 percent. He adamantly refused to explain why some of his millions were invested in the Cayman Islands, how much was there or whether any other funds were held offshore.

Under pressure from his rivals to release his income tax returns before the weekend — a demand first made by Perry in a debate on Monday — he told reporters it wouldn't happen. "You'll hear more about that. April," he said, a position he renewed during the debate to jeers from the audience.

Gingrich pursued an approach Perry used in the earlier debate.

"If there's anything that's in there that's going to help us lose the election, we should know before the election. If there's not, why not release it?" he said.

Gingrich released his own tax return during the day, reporting that he paid the IRS $613,517 in taxes on more than $3.1 million in income. He also donated about 2 percent of his income to charity.

His effective tax rate, roughly 31.6 percent of his adjusted income, was about double what Romney told reporters earlier this week he had paid.

Gingrich grappled with problems of a different, possibly even more crippling sort in a state where more than half the Republican electorate is evangelical.

In an interview scheduled to air on ABC News, Marianne Gingrich said her ex-husband had wanted an "open marriage" so he could have both a wife and a mistress. She said Gingrich conducted an affair with Callista Bistek — his current wife — "in my bedroom in our apartment in Washington" while she was elsewhere.