Should the lack of impersonation matter? It doesn't have to, but it does, especially when David Garrison's Nixon and Bryce Pinkham's Robert Kennedy are instantly identifiable caricatures. Cox has brusque, punchy energy. He can thunder with a king's power and howl with a titan's rage. At other times he's more like an executive who's sick and tired of boardroom fighting but not ready for his severance package. What Johnson actually was is hard to pin down - a hollow colossus, a giant ego, a black hole of need and want, a master manipulator, a bleeding heart. But he was neither king nor salesman: He was an American president. Somehow he's gotten away from this play.