Over the last three months, Trump watchers have noticed that former House speaker and 2012 Republican presidential candidate Newt Gingrich has been consistently advocating on Trump’s behalf in the media, on Capitol Hill, among K Street power brokers, and on social media. In fact, Gingrich has morphed into Trump’s unofficial ambassador for GOP peace and unity, while also seeking converts in hostile territory. Gingrich is the most recognized and respected member of the GOP establishment who is defending the insurgent candidate — even as Trump rails against that same establishment. But now, it has become apparent that Gingrich is waging...