Newt Gingrich vowed on Friday to campaign for the 2012 Republican presidential nomination on his own terms, saying he would do “whatever it takes” to remain in the race despite the exodus a day earlier of nearly his entire senior staff. “There is a fundamental strategic difference between the traditional consulting community and the kind of campaign I want to run,” Mr. Gingrich said. “Now we’ll find out over the next year who’s right.” Even as some prominent Republicans, including Gov. Terry Branstad of Iowa, questioned his viability, Mr. Gingrich made plans to deliver a foreign policy speech in Los...