At 5 p.m., an interfaith coalition will take the steps of City Hall for a second public worship, with prayers from Baptists, Catholics, Muslims, Jews and others. The Rev. Thomas Perchlik, the Unitarian organizing the effort, has even asked an atheist to share his reflections.
Mayor Dan Canan and several other civic leaders plan to attend both events. And Keller pronounces himself pleased with that solution.
"Everybody can do their own thing," he said.
But many in the community are troubled by the split.
"It's ridiculous. Prayer is prayer," said Mark DiFabio, 50, an advertising salesman.
"Prayer is for everybody," agreed Ella Holloway, 47, a cafeteria manager.
In recent months, Faiz Rahman, a local Muslim leader, has listened with unease as President Bush has from time to time used the rhetoric of evangelical Christianity to frame his vision for the nation. Rahman believes such language alienates citizens of other faiths.
He says he was "shocked" to hear a similar tone emerge in Muncie - a city where evangelical Baptists prayed in a mosque, side by side with Muslims, to show solidarity a few days after the Sept. 11 terrorist attacks.
"You'd expect this in another country, in a theocracy somewhere, but not here," said Rahman, a professor of geography at Ball State University. He estimates that there are perhaps 300 Muslims in Muncie.
"If this is to be a National Day of Prayer, then all faiths should be represented," he said.
Established in 1952 to encourage Americans to pray for their political leaders, the National Day of Prayer is marked in thousands of worship services across the country - in churches, at school flagpoles and often in front of government buildings. In a proclamation honoring such events last year, Bush called the National Day of Prayer an opportunity "to honor the religious diversity our freedom permits."
Although Muncie is predominantly Christian - with at least 100 churches - a growing number of other faiths are represented.
In the 1920s, Muncie gained fame as "Middletown, U.S.A." - a heartland city that academics held up as a perfect mirror of American culture, complete with racism, anti-Semitism and an influential branch of the Ku Klux Klan.
Since then, sociologists and pollsters have returned again and again to take the pulse of the nation by studying Muncie and have found it a place of religious tolerance, where, as the local newspaper put it, "races and religions learned to coexist, if not to actually welcome each other's presence."
Keller's annual observance of the National Day of Prayer drew few objections through the 1990s; those who felt uncomfortable with public prayers to Jesus Christ simply stayed away.
This year, however, with religious tensions around the globe so sharp, several pastors active in an interfaith group began to push for a more inclusive ceremony. They wanted to recognize that there's a mosque in Muncie and a synagogue, and that the Hindu community is growing large enough to think about building a temple.
"All of America's dealing with the fact that we as a nation are becoming more diverse," Perchlik said.
Since Keller announced that he would not share the microphone, the editorial page of the Muncie Star Press has been swamped with letters - so far running about 2-to-1 against the idea of an exclusively Christian-led service.
Keller's supporters, however, are holding their ground. They believe they are on the one true path to salvation. They are certain their prayers, and theirs alone, will be heard. So they don't see the point of inviting other religious leaders to share the microphone on the steps of City Hall.
An interfaith service would be a meaningless "public show," resident Eric Miller wrote the newspaper.
As an evangelical minister, the Rev. Woody Noblitt sympathizes with such conviction. He considers Keller a friend. But he is also a member of the interfaith group. He plans to attend both services today. Both are advertised on the marquee outside his First Baptist Church.