Charles Dharapak, Associated Press
Republican presidential candidate, former Massachusetts Gov. Mitt Romney, stands with, from left, his wife Ann, obscured left, granddaughter Allie, son Tagg, son Matt, and granddaughter Chloe, as he speaks at his South Carolina primary election night reception at the South Carolina State Fairgrounds in Columbia, S.C., Saturday, Jan. 21, 2012. Former House Speaker Newt Gingrich won the Republican primary Saturday night.

WASHINGTON — Strong backing from conservative and religious voters and people fretting about the uncertain economy fueled Newt Gingrich's victory Saturday in South Carolina's Republican presidential primary, an exit poll of voters showed Saturday.

The figures also showed that for the first time, the former House speaker had grabbed two constituencies that his chief rival, Mitt Romney, prided himself in winning in the year's two previous GOP contests in Iowa and New Hampshire. By a decisive 5 to 4 margin, Gingrich bested Romney among voters looking for someone to defeat President Barack Obama this November, and he led Romney by nearly as much among those who considered the economy the top issue in picking a candidate.

Gingrich benefited most from the campaign's final, tumultuous week, the figures showed.

Just over half said they'd chosen a candidate in the last few days, and they backed Gingrich over Romney, the former Massachusetts governor, by 2-1. By a slightly stronger margin, the roughly two-thirds who said campaign debates were an important factor also supported Gingrich. There were two GOP debates in South Carolina during the past week.

In the last days of the campaign, Romney stumbled badly when asked repeatedly whether he will release his income tax returns. Gingrich endured an allegation by one of his two former wives, Marianne, that he had asked permission for an open marriage while he was having an affair with the woman who is his current wife, Callista.

That accusation seemed to take only a slight toll on Gingrich.

He got less than 10 percent support from people who said what they most wanted in a candidate was strong moral character, but these voters were less than 1 in 5 of those who showed up Saturday at the polls. And Gingrich did slightly better than Romney among women and polled a bit more strongly among married than unmarried females.

Gingrich won healthy margins among the state's conservatives, who comprise more than 6 in 10 voters in the state, one of the country's reddest. While those results were bad news for Romney, they were even more damaging to Rick Santorum, the former Pennsylvania senator who has been dueling with Gingrich to become the GOP's conservative champion and alternative to Romney.

Gingrich won among conservatives and tea party supporters by nearly 2-1 over Romney. Santorum was slightly behind.

Nearly two-thirds of voters Saturday said they are born again or evangelical Christians, and they backed Gingrich over Romney by 2-1 also.

More telling, 6 in 10 voters said it was important that their candidate share their religious beliefs. Nearly half of such voters backed Gingrich, while only around 1 in 5 chose Romney or Santorum.

About 8 in 10 voters said they were very worried about the direction of the country's economy, and they picked Gingrich over Romney by about a 4-3 edge.

South Carolina's unemployment rate of 9.9 percent is worse than the national average, and the exit poll provided evidence of the state's economic pain. About 3 in 10 said someone in their household has lost a job in the past three years. And about 1 in 5 said they are falling behind financially — about double the proportion who said so in exit polling in the state's 2008 GOP presidential primary.

Romney's earlier career heading Bain Capital, a venture capital firm, clearly wounded his prospects. During much of the campaign, Gingrich and others accused Romney and his company of killing jobs in the companies they bought and restructured.

Those blows showed on Saturday. According to the exit polls, Gingrich and Romney broke about even among the 6 in 10 voters who said they had a positive view of Romney's activities at Bain. But among those who viewed Romney's work negatively, half picked Gingrich and almost none backed Romney.

Underscoring how poorly Romney fared in South Carolina, only about 4 in 10 voters Saturday said they could enthusiastically back Romney should he eventually win the GOP nomination.

Romney's defeat was so sweeping that he lost to Gingrich among voters of every age. The only income group that Romney won was people making above $200,000 a year — 1 in 20 of those who voted Saturday.

The exit poll also showed that around two-thirds of voters approve of the job Nikki Haley is doing as governor, a job she won with strong tea party support. Haley endorsed Romney but 7 in 10 tea party backers gave her high marks anyway.

The survey was conducted for AP and the television networks by Edison Research as voters left their polling places at 35 randomly selected sites in South Carolina. The survey involved interviews with 2,381 voters and has a margin of sampling error of plus or minus 3 percentage points.

Associated Press global polling director Trevor Tompson contributed to this report.