A lively three-way Republican primary is taking shape in Michigan, where attorney Brian Rooney, who made his candidacy official on Thursday, is running against former Rep. Tim Walberg and rancher-real estate investor Marvin Carlson. The winner of the GOP primary will face Rep. Mark Schauer next November. The prospect of taking on Democrat Schauer is pretty inviting to Republicans in the 7th District, which includes the cities of Battle Creek and Jackson. Another GOP prospect has been considering getting in the race, too -- Bill Martin, CEO of the Michigan Association of Realtors. However, sources on the ground say Martin...