Some of President-elect Barack Obama’s supporters are upset that he chose Rick Warren to give the invocation at his inauguration. They should not be surprised. He promised as a candidate that he would try to change the divisive tone of America’s politics. But sometimes, to paraphrase one of campaign slogans, “change” is easier to “believe in” than to act upon.

Groups like the Human Rights Campaign and People for the American Way oppose Warren, the pastor of California’s Saddleback Church and best-selling author of “The Purpose Driven Life.” They don’t like Warren’s opposition to abortion or his endorsement of Proposition 8, the ballot measure that amended California’s constitution to limit marriage only to a man and a woman.

Obama, like other leading Democratic presidential candidates, favors abortion rights and gay rights, although not gay marriage.

And Obama’s outreach to evangelicals is nothing new. As he said in a Thursday news conference in Chicago, his invitation continues a dialogue with evangelical Christians that began before his campaign. The former Chicago community organizer has long criticized Democrats for passing up golden opportunities to reach out to church folks of all political leanings.

Obama’s effort took on new life when Warren invited Obama to appear before his congregation at Saddleback Church. Although some gay activists and other left-progressives might try to dismiss him as a hard-line troglodyte, Warren actually is a pragmatic moderate compared to right-wing evangelical activists like Pat Robertson or the late Rev. Jerry Falwell. New-wave televangelists like Warren have built huge followings by toning down the politics to issues on which more of us can agree – like fighting AIDS, poverty and environmental pollution.

Both Warren and Obama share a pragmatism that is characteristic of the generation that came of age since the 1960s. Don’t let ideological areas in which you disagree get in the way of the many areas in which you agree.

“We’re not going to agree on every single issue,” Obama said at a Thursday news conference in Chicago, “but what we have to do is be able to create an atmosphere where we can disagree without being disagreeable, and then focus on those things that we hold in common.”

That’s a lofty but worthy goal. Obama won election by appealing to common interests that all Americans share. He was helped ironically in this cause by an economic crisis that has become the mother of all unifying national headaches.

Those who don’t know Obama well were similarly puzzled when he appeared at Saddleback Church in a program with his Republican opponent, Sen. John McCain. Obama could have done better that night, I wrote at the time. I thought his response to Warren’s question about when life begins by saying that’s “above my pay grade,” was a bit too flip to win the hearts of the anti-choice flock.

Yet I think Obama probably knew better than pundits like me how important it was not that he gave all the best polished answers to Warren’s questions but that he showed up at all. Unlike previous Democratic candidates who shied away from church congregations unless they were, say, liberal blacks, Obama undoubtedly reached a lot of persuadable voters that night and reduced the concerns of many who needed to know him better.

Barack Obama’s conflict over his friend Rick Warren vs. his friends in the gay rights community reminds me of the old adage about moderation: If you play in the middle of the road, you’ll get hit by both sides.

By now, Obama has grown accustomed to getting hit by the religious right for favoring abortion rights and by the left for opposing gay marriage. But he promised to try to carve a new middle ground in our politics and our big social divides. Advocates of gay marriage should not make too much of the outreach to Warren. If you want to change people’s minds, you need to reach out first to those who, at least are willing to give you a listen.

Clarence Page is an columnist for the Chicago Tribune. E-mail cpage@tribune.com.