Newt Gingrich, the first candidate to campaign in Delaware, came here Monday night pushing his $2.50-per-gallon-of-gas energy plan and jabbing President Obama about comments caught on an open microphone with outgoing Russian President Dmitri Medvedev. Gingrich said that Obama’s suggestion that he would have more flexibility to negotiate on nuclear arms after winning the 2012 election, was “destructive of American interests.” “This is a president who is amazingly destructive of American interests, something by the way of which we were reminded of today, when he didn’t know there was an open microphone,” he said to meeting of local Republican groups....