WASHINGTON -- Hoping to prod Barack Obama into appearing on its show, "Fox News Sunday" launched the "Obama Watch," a weekly update on the number of days the Democratic presidential candidate has failed to appear on the program. Host Chris Wallace said Sunday that Obama promised him in March 2006 that he would appear, but the Illinois senator has since demurred. Since then, New York Sen. Hillary Rodham Clinton, Obama's rival for the Democratic presidential nomination, has been a guest at least twice since then, and Sen. John McCain, R-Ariz., the likely Republican nominee for president, has shown up at...