Chris Christie backs off from 'tit-for-tat' with Trump: 'I'm bigger and better than that'

IOWA CITY, Iowa — A day after Republican presidential front-runner Donald Trump opened a broad attack on New Jersey Gov. Chris Christie at a campaign stop in New Hampshire, Christie responded by suggesting that he was above engaging the bombastic real estate mogul. "All I have to say to Donald is, Happy New Year and I'll…