The pick was seen as something of an upset, given Keyes' higher national profile. Known for his fiery stem-winders, Keyes is a two-time GOP presidential candidate who abandoned the Republican Party this month to join the Constitution Party, which believes in limited government and is committed to ending abortion and bringing American troops home from Iraq.

But Baldwin's roots in the Constitution Party run deeper. He was the party's 2004 vice-presidential candidate, and party members said his stands were more in line with party thinking. ...