Tolerating—or even encouraging—dissent at the central bank is one of several moves by Powell that could fortify the 112-year-old institution against the Trump administration’s unrelenting efforts to take control of monetary policy. Further removed from the public eye, but perhaps no less important, is the long-running charm offensive Powell has been waging on Capitol Hill, a campaign that’s intensified in recent months as the president and administration officials have ramped up their attacks on Powell and other members of the governing board.