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Mitt Romney's struggle with white evangelical voters doesn't bode well for him as he moves through the GOP presidential primary, with Mississippi and Alabama just ahead.

In the five states so far where born-again Christians were a majority of GOP primary voters, Romney has trailed either Rick Santorum or Newt Gingrich among evangelicals by an average of 20 points, according to exit polls. About 4 in 10 born-again voters who were asked said it was deeply important that a candidate share their religious beliefs.

Still, exit polls also show an opening for Romney to draw a bit more of the evangelical vote. In Ohio and Tennessee, evangelicals who said shared religious beliefs are less important when choosing a candidate were significantly less likely than other evangelicals to see Romney as too moderate.

The key question for Romney is whether enough of these evangelicals are present in the contests ahead to make any difference for his candidacy.

In the 2008 Republican presidential primary, about three-quarters of Republicans in Mississippi and two-thirds in Alabama identified themselves as white evangelicals. Primaries in Mississippi and Alabama are set for Tuesday, with Louisiana to follow on March 24.

John Green, a University of Akron political scientist who analyzes religion and voting, said he noticed that Romney generally does better, although not well, among evangelicals in larger metropolitan areas. These urban born-again voters are found in greater numbers in states where Democrats and Republicans are more competitive, such as the Midwest. Kansas is scheduled to hold its caucuses Saturday, and Missouri and Illinois contests are scheduled near the end of the month.

However, pragmatism may win out even among some Bible Belt Christian voters, since large groups of Republicans have said repeatedly in exit polls that they are seeking a candidate who can beat President Barack Obama in the general election.

"What these numbers suggest is that he has a chance to expand his support among evangelicals," Green said. "I don't know exactly what it is that Romney would have to say to persuade them, but it doesn't seem like his religion or the things he's been saying are necessarily a barrier."

It's impossible to know how much Romney's Mormonism has been a factor in his weaker performance.

On politics alone, many Republicans are wary. Romney once supported legalized abortion, which he now condemns, and enacted a health care coverage program as governor that many conservatives consider government overreach. In Ohio on Super Tuesday, nearly half of evangelicals said Romney's positions on the issues were not conservative enough.

Romney is also is lacking in the kind of charisma that has buoyed other candidates, especially in the South, said Jim Guth, a political scientist at Furman University in South Carolina. "Evangelicals like their leaders with a little zing — and that Romney doesn't have," Guth said. "And, of course, his social milieu and cultural expression just doesn't match theirs very well."

Many Christians do not consider Mormons part of historical Christianity, although Mormons do. Republicans who say Mormonism is not Christian are less likely to support Romney for the GOP nomination, according to a November 2011 survey by the Pew Center's Forum on Religion & Public Life.

Conservatives who consider religion when choosing a candidate have had several other options in the large field of candidates for the Republican nomination. Santorum and Gingrich are Roman Catholics who heavily emphasize religion and moral issues on the campaign trail, although Gingrich's personal history, including three marriages, has cost him some conservative support. The same Pew survey, however, found GOP voters would overwhelmingly back Romney in a general election against Obama. .

In Romney's 2008 bid for the presidential nomination, he openly courted evangelical leaders and directly confronted concerns about his Mormonism, including a major speech in which he promised "no authorities of my church" will influence his policies. This election year, Romney barely mentions his religion unless an issue arises while campaigning.

Instead, he has tried to appeal to religious conservatives by stressing his shared values with them on concerns such as traditional marriage, especially as social issues took prominence in the campaign due in part to the ascendance of Santorum. Campaigning Thursday in Huntsville, Ala., Santorum called the state the "heart of conservatism."

If Romney too heavily emphasizes social policies, he would also draw attention to his former stand in favor of legalized abortion.

Mark DeMoss, a public relations veteran and evangelical adviser to the Romney campaign, said there is no plan to change that strategy on religion as the primaries move through heavily evangelical states in the weeks ahead. He said the former governor will keep his focus on "the state of the economy and uncertainty about jobs."

"I think those issues cross all segments of voters," DeMoss said.

This means missed opportunities for connecting with religious voters. DeMoss said Romney doesn't visit church services as part of his campaign. The weekend before Super Tuesday, Santorum and his family attended Sunday worship at a Southern Baptist mega-church in Tennessee, where the pastor invited them to stand before the congregation and receive a blessing, according to Associated Baptist Press. Romney finished second to Santorum in Tennessee.

"Churches are largely the social and cultural centers in these communities and the minister usually has the largest microphone, so building real and authentic relationships with people of faith is pretty essential," said Burns Strider, a Mississippi native and adviser on faith outreach to Democrats, including Hillary Rodham Clinton when she was seeking the party's 2008 presidential nomination. "It doesn't mean it requires Sunday worship services, but there are plenty of other opportunities."

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AP Religion Writer Rachel Zoll reported from New York. AP Deputy Director of Polling Jennifer Agiesta reported from Washington.