MANCHESTER, N.H. — Former New Jersey Gov. Chris Christie wondered if the Republican field has what it takes to stop former President Donald Trump. Christie challenged Republicans to find someone who can do to Trump “what I did to Marco” Rubio — a callback to his 2016 debate-stage evisceration of the Republican senator from Florida — “because that’s the only thing that’s going to defeat” Trump. “You have to be fearless, because he will come back — and right at you,” Christie said. “And that means you need to think about who’s got the skill to do that, and who’s...