Dr. Tom Coburn, the plainspoken obstetrician from Muskogee, Okla., was back in Washington briefly last week. Republican senators greeted him with mixed emotions. He is their best hope for keeping an Oklahoma seat Republican in the closely divided Senate. The bad news is, he would be as prickly as he was during his six years in the House (1995-2000). Coburn's problem is that he takes seriously the professed Republican agenda: limited government, entitlement reform and anti-abortion advocacy. He was a rare sincere GOP supporter of term limits, leaving the House after three terms as he promised to do. The result...