Sarah Palin was in Iowa Tuesday. Michele Bachmann announced her candidacy there on Monday. For reporters, that's a coincidence impossible to resist; scads of stories are being produced comparing the two women. Comparisons between Palin and Bachmann are, at one level, apt. Both are women who align most closely with social conservatives. Both are outspoken defenders of their chosen causes whose rhetoric occasionally gets them into hot water. But over the past few months, Bachmann has proven she is different in important ways from Palin - differences that make her the more viable of the two when it comes to...