Throughout his Hall of Fame baseball career, Jim Bunning was famous for the brush back pitch: a fastball inside to a batter crowding the plate. Now Mr. Bunning, a Republican from Kentucky who is retiring after this year, is throwing a political brush back in the Senate on behalf of fiscal responsibility.

And all hell has broken loose. Mr. Bunning has dared to put a hold on a $10 billion spending bill to extend jobless insurance and fund transportation projects. Mr. Bunning says he won't yield until the Senate finds a way...