Signaling a new aggressiveness, aides to Sen. John McCain (D-Ariz.) said Saturday that he is going up immediately with an ad called "Troops" criticizing Sen. Barack Obama (D-Ill.) for canceling plans to visit wounded troops at a U.S. military hospital in Germany. The 30-second ad is to run during NBC's "Saturday Night Live" in Denver. Colorado is one of this election's most important swing states. On Sunday it will air in the Washington market and in Harrisburg, Pa., another key swing state. An announcer says: "Barack Obama never held a single Senate hearing on Afghanistan. He hadn't been to Iraq...