Zandstra, who is making his first run for office, said he was taking leaves of absence from his posts as program director at the Acton Institute for the Study of Religion & Liberty and as a minister at Hillside Community Church, a Christian Reformed church in the Grand Rapids suburb of Cutlerville.
"Why in the world would I walk away from both of my day jobs to do this? It's because ... ideas matter. Our culture, our economy and our international engagement matter," he told about 100 supporters who gathered at Cornerstone University.
Zandstra, 40, is the second minister to enter the GOP race, following the Rev. Keith Butler, a former Detroit city council member who is at Word of Faith International Christian Center Church in Southfield. Troy industrial engineer Bart Baron is also seeking the nomination.
The field also could include Michigan Secretary of State Terri Lynn Land (search) and Jane Abraham (search), a former state GOP political director and the wife of former U.S. Energy Secretary Spencer Abraham.
The primary is scheduled for Aug. 8, 2006.
The winner will face Stabenow, who became the Michigan's first woman senator when she was elected in 2000.