In the constellation of Protestant churches, the United Church of Christ is far from the biggest, wealthiest or best-known.

But Democrat Barack Obama is making time in his presidential campaign Saturday to address the denomination he joined two decades ago in Chicago, hoping his presence will signal to a broader audience of churchgoing Americans that he's truly one of them.

"If he's a nominee, he's going to have to reach out to people of faith somehow and he has to do that in a way that doesn't alienate the secular, liberal crowd," said Laura Olson, a Clemson University professor who specializes in religion and politics. "If people can say, 'Here's what Obama said to the UCC,' and quote from that down the road, that could help him win over people from moderate to progressive faith."

There's no question that he'll get a rousing welcome at the national meeting in Hartford, Conn. — and not just because he's the best-known face in the denomination.

The church, with about 1.2 million members, is considered the most liberal of the mainline Protestant groups. In 1972, the UCC was the first to ordain an openly gay man. And two years ago, the church endorsed same-sex marriage, the largest Christian denomination to do so.

Obama believes that states should decide whether to allow gay marriage, and he opposes a constitutional amendment against it. Whatever differences he has with UCC policies, conservative Christian bloggers are already linking him to what they call the "unbiblical" teachings of his church. Theological conservatives believe gay relationships violate Scripture, while more liberal Christians emphasize the Bible's social justice teachings.

The UCC's "religious faith is so tied to this-worldly concerns for justice and political progress that the political is religious to them," said Michael Cromartie, an evangelical and vice president of the Ethics & Public Policy Center, a conservative Washington think-tank.

Critics have also tried to tie Obama to the left-leaning views of his pastor and spiritual mentor, the Rev. Jeremiah Wright Jr.

Obama came to the UCC at age 26 through the Trinity United Church of Christ in Chicago, a self-described "unashamedly black" church that emphasizes the importance of black family life and community service, while criticizing the U.S. war in Iraq.

Responding to the attacks, Obama made a last-minute decision not to have Wright speak at the senator's presidential announcement in February. Wright has said that Obama later apologized for the decision.

Kenneth Wald, a University of Florida political scientist who studies religion and politics, called the criticisms of Obama's congregation "trivial."

And Democrats in no way expect to peel away the theological conservatives who form a core of the GOP voting base. Instead, Obama and other Democrats hope to attract evangelicals, along with other religious voters, who view the traditional focus on abortion and marriage as too narrow.

"It's not that the politicians are finding religion," said Mike McCurry, a former spokesman for President Clinton who is an active Methodist and member of the Democratic National Committee's faith advisory council. "It's that the politicians are understanding that their spirituality is part of the composite picture of what they need to bring to the electorate."

Much has been made of Obama's skill in speaking about faith, even as his top Democratic rivals for the party's nomination, Sen. Hillary Rodham Clinton and former Sen. John Edwards, have been remarkably open about their own religious beliefs. Clinton and Edwards are both Methodists.

In June 2006, before he had declared his candidacy, Obama spoke at a conference organized by Call to Renewal, a liberal evangelical group, urging people to "tackle head-on the mutual suspicion that sometimes exists between religious America and secular America."

To make the point, he cited an example of what he now considers his own past intolerance of people of faith who oppose abortion. The Illinois senator favors abortion rights. McCurry, who backs Clinton for president, called that speech "awfully compelling."

Josh DuBois, religious affairs director for the Obama campaign, said he expected the candidate to address similar themes on Saturday.

DuBois said "I might have been a little worried" a couple of years ago that an Obama appearance before the liberal UCC would provide fodder for the senator's critics.

But DuBois, who worships in an Assemblies of God Pentecostal church, contends that UCC members are much more diverse than people know. The denomination claims 10 members in Congress — five Democrats and five Republicans.

"I'm comfortable with the fact that he's embracing a church that he's been a part of for 20 years," DuBois said, "for wanting to stand with his church and not distancing himself from this Christian denomination, just because he's on a presidential campaign."