But temperament is not irrelevant in a leader. A pronounced trait such as anger puts a particular burden on a political figure's inner circle of friends and advisers. They can choose to tap the brakes or push the accelerator -- to moderate and channel a leader's tendencies or feed those faults for their own purposes. Aides to Richard Nixon gained favor by stoking his paranoia. Some of Bill Clinton's staff enabled his self-indulgence and recklessness.
In at least one instance, McCain's temper seems to have clouded his judgment. In February 2000, after being criticized by religious conservatives, McCain gave a very angry speech in Virginia attacking leaders of the religious right as "agents of intolerance," comparing them to Louis Farrakhan, accusing them of having "turned good causes into businesses," calling them "corrupting influences on religion and politics" who "shame our faith, our party and our country." It was a tantrum disguised as a campaign event. Key advisers around McCain enflamed this pointless anger instead of dousing it. These days, Sen. Joe Lieberman -- one of the most decent and temperate men in Washington -- apparently is playing the role of McCain's fire marshal.
On the evidence of the Virginia speech, McCain's worst temptation is not anger but moral arrogance. Opponents are not merely wrong; they are venal, self-interested and corrupt. In a righteous cause, McCain can be self-righteous.
But this weakness, as is often the case in politics, is inseparable from McCain's political appeal. Recent weeks have raised the question: Can the detached, intellectual Barack Obama draw clear lines of outrage on the anti-American rhetoric or violent radicalism of some of his associates? When it comes to the largest matters -- public officials who violate the public trust or enemies who threaten America -- no one can accuse McCain of insufficient moral outrage.