On Saturday in Peterborough, it was standing room only at his 100th town-hall meeting in New Hampshire, as hundreds of people packed into a building to hear him speak. The police had to seal the doors, keeping many supporters outside chanting Mr. McCain’s name.  The McCain events follow a pattern. There are the corny opening jokes and the recitation of the reasons he thinks he should be president, items he rushes through so rapidly that they are sometimes a bit garbled. But those are the mere preludes to the main event, his spirited exchanges with voters.  Mr. McCain is so eager to mix it up that even when a supporter challenges him, he seems to look for ways to tell them things they do not want to hear.  If someone is critical of President Bush, he tells them where the president deserves credit: for his work on AIDS in Africa or for the fact that the United States has not been attacked since Sept. 11, 2001. But when another voter blames the news media or Democrats for the perception that the war in Iraq was mismanaged over its first four years, he will point to Donald H. Rumsfeld, the former secretary of defense, and Mr. Bush himself.  On climate change, an issue that he has fought long to address, he will tell an admirer that he will push for the expanded use of nuclear power, something many environmentalists oppose.  After an event on Friday at a company that makes equipment for the military, Mr. McCain chose to rail against the “military-industrial complex.” Later, he said, “Sometimes I go too far.”  He said an angel on one shoulder begged him to pipe down while a devil on the other goaded him on. His best events are when the devil gets the better of him.  He frequently tells voters that it was the town-hall format — inspired by one event in the 2000 campaign — that led him to grasp the threat of global warming.  There is chance involved in these exchanges: when the questions are dull, it can sap the energy in the room. But on Thursday night, at the opera house in Derry, all the elements came together, including his confrontation with an opponent of the war and an emotional exchange with Allie Nault, 10. Allie, articulate for her age and adorable in her Red Star Twirler outfit, said pupils in her class had been asked to select a favorite presidential candidate.  She said she had chosen Mr. McCain. Allie made her way to the front and hugged the 71-year-old senator, tears in her eyes.  With the audience in his hands at that point, Mr. McCain moved on to the man with the white beard in the corner of the room, calling on him by joking that he had not realized Ernest Hemingway was in the crowd.  When the two were done sparring over Iraq, the man was won over enough to urge Mr. McCain to trounce Mitt Romney, his chief Republican rival.  A version of this article appears in print on , on Page 117 of the New York edition with the headline: McCain Mixes It Up on a Town-Hall Tour of New Hampshire. Order Reprints| Today's Paper|Subscribe
John McCain has been holding town hall meetings in New Hampshire for much of the last year, including one on Thursday night, during the Iowa caucuses.