Is McCain's Sharp Tongue Achilles Heel?" ''Fuck you!' he shouted at Texas Sen. John Cornyn last year. ''Only an asshole would put together a budget like this,'' he told the former Budget Committee chairman, Sen. Pete Domenici, in 1999. ''I'm calling you a fucking jerk!'' he once retorted to Iowa Sen. Chuck Grassley. With Cornyn, he smoothed things over quickly. The two argued during a meeting on immigration legislation; Cornyn complained that McCain seemed to parachute in during the final stages of negotiations. ''Fuck you. I know more about this than anyone else in the room,'' McCain reportedly shouted.... McCain has even blown up at volunteers and, on occasion, the average Joe... ''Thanks for the question, you little jerk,'' he said last year to a New Hampshire high school student wondering if McCain, at 71, was too old to be president. Other times, his ire is all too real. This has prompted questions about whether his temperament is suited to the office of commander-in-chief or whether it might handicap him in a presidential campaign against either Barack Obama or Hillary Rodham Clinton, who are not known for such outbursts. ''I decided I didn't want this guy anywhere near a trigger,'' Domenici told Newsweek in 2000."