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An evangelical group has begun a weeklong advertising campaign in Iowa criticizing Senate Majority Leader Bill Frist (search) for backing expanded embryonic stem cell research.

"We know Iowa is a way to get everybody's attention," said Gary Cass, head of the Florida-based Center for Reclaiming America. "Our hope is Senator Frist will hear from Iowans and they are kind of a bellwether state in the heartland."

Iowa is a critical state in the presidential nominating process and Frist is considered a potential candidate for the Republican nomination in 2008.

In the ad, which shows a photo of a smiling baby, an announcer says: "Senator Frist: we cannot save innocent lives by destroying them. Tell Senator Frist to stand with President Bush and oppose research that destroys human embryos."

Cass said the ads began airing Thursday on television stations in the Des Moines area and local radio stations around the state. The group is spending about $50,000 but could expand the campaign if more money is raised. It also sent e-mails to a national listing of 500,000 social conservatives.

Nick Smith, a spokesman for the Tennessee senator, said Frist "understands that there are many opinions on this issue and he respects those opinions. However, after long thought, he has made his decision based on principle and believes it holds great promise in helping many people."

Frist angered many social conservatives when he endorsed legislation that would provide federal funds for expanded stem cell research.

"Senator Frist made a tragic and grave error in endorsing public funding of research that destroys human life," Cass said.