With Congress's approval rating at record lows, the time is ripe for a slam campaign. Barack Obama won't do it, since his Democratic colleagues are running the joint. But it's a huge opportunity for Mr. McCain, who could play Congress's failings off his promises for reform. Mr. McCain could take encouragement from history. Harry Truman managed a 1948 victory by trashing the "Do Nothing Congress." Upstart Barry Goldwater in 1952 told Arizonans that Majority Leader Ernest McFarland represented the mess in Washington, and snatched the Democrat's seat. Tom Daschle followed McFarland, after being pilloried for turning the Senate into a...