Chris Christie can speak truth to Trump. And his latest pitch to American voters? Who else has the guts to do it in public, because according to him everybody is doing it in the shadows. “Some people say I should drop out of this race,” the former New Jersey governor says during a 30-second ad set in front of a stark black background. “Really? I’m the only one saying Donald Trump is a liar.” POLL: Should Trump be allowed to run for office? It’s the words of the presidential hopeful, in an ad buy debuting on CNN, that allegedly cost him seven figures to circulate on New Hampshire airwaves. Chri…