The two leading Republican candidates not named Donald J. Trump who most need a victory in the New Hampshire primary have wooed voters here by promoting their experience, their tough-mindedness and their seriousness. Now, as Gov. Chris Christie of New Jersey and Jeb Bush grasp for some way to dissuade the proud New Hampshire electorate from supporting Mr. Trump, they are turning to a new, blunter instrument: guilt. "America is counting on you," Mr. Christie said Sunday night in the century-old town hall here, his 40th question-and-answer session in the state. He repeated himself a few sentences later, in case...