Great legislators do not make great presidents. In fact, they rarely make presidents of any kind. The greatest senators and representatives in American history – Henry Clay, John C. Calhoun, Daniel Webster, Thomas B. Reed, Joseph Cannon, and Sam Rayburn – never reached the White House. Those lawmakers who did get there – starting with James Madison and continuing through George Bush – failed to distinguish themselves at one end or the other of Pennsylvania Avenue, often both.

There is a reason for this. The legislative mentality is not the executive mentality. If anything, the former militates against the latter. The successful legislator is an accommodator, a compromiser, a dealmaker, a person who acknowledges that in a democracy differing viewpoints can be equally valid, by the mere fact that they are held by different citizens, and for that reason must be taken into account. The successful executive, on the other hand, is a leader, a decisionmaker, a buck-stopper, a person who embodies not the least common denominator of the polity but the greatest common multiple. Executives get paid to make hard choices, legislators to prevent hard choices from having to be made.

Lyndon Johnson could have been a great legislator. He had Sam Rayburn for a tutor; more important, he had the right instincts. He delighted in discovering what different people needed from government on a particular issue, and in employing what he discovered to fashion a bill a majority could get behind.