Rick Santorum (AP)

LIVONIA, Mich. (AP) -- Republican presidential candidate Rick Santorum is calling for a bigger role for religion in the public square and faults President Barack Obama for marginalizing faith.

Speaking to a suburban Detroit chamber of commerce on the eve of Tuesday's primary, Santorum says freedom of religion has been "turned on its head."

The former Pennsylvania senator told about 300 people in Lavonia: "I'm for separation of church and state. The state has no business telling the church what to do."

Campaigning as the stricter conservative, Santorum is locked in a fierce battle in Michigan with former Massachusetts Gov. Mitt Romney.

Romney, who stirs doubts among some conservatives, recently has sought to undermine Santorum's conservative credentials by pointing to Senate votes he acknowledged were against his principles.