Tom Coburn may be indispensable to the Republicans' effort to hold on to their majority in the U.S. Senate in November. "He is their best hope for keeping an Oklahoma seat Republican in the closely divided Senate," wrote conservative pundit Robert Novak. Coburn was swept into Congress as a member of the Republican class of 1994 that gained control of the House for the first time in 40 years and installed Newt Gingrich as speaker. "He really drank the Kool-Aid with the class of '94; he was one of the real far-right guys," says Kenneth Hicks, a political science professor...