“I’ll do what I need to do when I need to do it,” Christie told the Trump critic on Thursday. “Trust me on this: I have a plan.”

If current polls are accurate, the New Jersey governor is part of a large group of candidates fighting it out for second place behind Trump ahead of the Feb. 9 primary in New Hampshire. The goal for Trump’s opponents is to become the main alternative to the maverick front-runner coming out of the Granite State.

During the town hall in Derry, Christie suggested that one of his potential tacks against Trump is the businessman’s lack of political experience. He questioned whether Trump could get things done in government, especially his major proposals like a wall along the U.S.-Mexican border.

“I tell everybody who goes to a Donald Trump event, if you get to ask a question, just ask him ‘how?’ ” Christie said. “I don’t care which of the things he talks about just ask him, ‘How? How?’ “