I wrote on him for NRODT a couple of years ago. Key graf:

Bush’s top staff, however, is definitely not happy with Milbank. He holds one of the premier jobs in political journalism — White House correspondent for the Washington Post — yet he approaches his beat with anything but balance, as his attempt to shape public perceptions of the Woodward book demonstrates. The bias comes as no surprise, given his profession. In a recent Pew Research Center survey of national journalists (such as Milbank), 34 percent labeled themselves “liberal” and only 7 percent labeled themselves “conservative.” (Most say they are “moderate” — which is how Dan Rather describes the New York Times.) Even in this crowd of semi-closeted Democrats, however, Milbank stands out as probably the most anti-Bush reporter currently assigned to the White House by a major news organization.