Barack Obama spent a lot of political energy recently explaining his faith because of the hubbub over controversial comments by his pastor, the Rev. Jeremiah Wright.

He may have a chance to talk about those issues at length Sunday.

Rick Bowmer/AP (ENLARGE)

Democratic presidential hopeful Sen. Barack Obama will field questions about faith and values in a nationally televised forum Sunday night.

Charles Dharapak/AP (ENLARGE)

Democratic presidential hopeful Sen. Hillary Clinton will field questions about faith and values in a nationally televised forum Sunday night.

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His competitor in the Democratic presidential primary, Hillary Clinton, may get a chance to ratchet up the heat.

The two will field questions in a nationally televised forum on faith, values and issues, such as feeding the hungry.

The organizing group, Faith in Public Life, which includes Christian, Jewish and Muslim leaders, also invited Republican candidate Sen. John McCain. He declined, citing a scheduling conflict.

"It would have been more important if McCain had decided to participate," said David Gushee, a forum organizer and professor of Christian ethics at Georgia's Mercer University.

But it will still have an impact on the presidential election, he said.

Messiah College, an evangelical Christian institution near Harrisburg, Pa., is the host site.

Obama and Clinton hope to score points before the Democratic primary April 22.

McCain may be ducking and hoping to shore up support of the faithful nearer the November election, but there is a risk in missing the forum, said Michael Lindsay, a Rice University professor and author of "Faith in the Halls of Power: How Evangelicals Joined the American Elite."

Votes from big segments of evangelicals and Catholics appear up for grabs.

"Pennsylvania is a state where conservative Catholics and Protestants are significant swing voters. I think there is a definite segment of the evangelical vote who is trying to make up their minds. So it may be politically unwise. But [religion] is not McCain's strong suit. So it is not surprising he is trying to stay under the radar," Lindsay said.

McCain has been less effusive about his faith than the Democrats. He feuded with high-profile conservative Christians such as the late Rev. Jerry Falwell in 2000, and some evangelicals with national followings, such as James Dobson of Focus on the Family, have snubbed him this time.

A theme emerging in the 2008 campaign is that Democrats are more comfortable talking about their faith than McCain, said Gushee, who wrote "The Future of Faith in American Politics: the Public Witness of the Evangelical Center."

That is a change from 2004 when Bush was at ease and Sen. John Kerry the one who seemed stilted when talking about how religion influenced their lives and thinking.

Gushee said the forum members wanted to broaden the discussion beyond the gay marriage and abortion fights that dominated the religion culture wars of the 1980s and 1990s. They are including issues now attracting concern from the faithful, such as global warming, poverty, genocide in Darfur and the torture of prisoners.

Father Larry Snyder, head of Catholic Charities USA and another forum member, said they also wanted people from all the major religions and denominations to take part in the conversation.

"I think people of faith are realizing that if we come together and act out of common values we can have more an impact," he said.

The Compassion Forum will be broadcast at 8 p.m. Sunday by CNN. It will be moderated by Newsweek editor Jon Meacham.