GREAT MINDS THINK ALIKE: Megan McArdle:

Jane’s Law: The devotees of the party in power are smug and arrogant. The devotees of the party out of power are insane.

David Brooks:

Something similar seems to be happening domestically between Republicans and Democrats. It’s not just that members of the two parties disagree. It’s that the disagreements have recently grown so deep that liberals and conservatives don’t seem to perceive the same reality. Whether it is across the ocean or across the aisle, powerlessness corrupts just as certainly as power does. Those on top become overly self-assured, emotionally calloused, dishonest with themselves, and complacent. Those on the bottom become vicious. Sensing that their dignity is perpetually insulted, they begin to see their plight in lurid terms. They exaggerate the power of their foes. They invent malevolent conspiracy theories to explain their unfortunate position. They develop a gloomy and panicked view of the world.

Powerlessness corrupts, indeed.

UPDATE: This post by Armed Liberal provides an interesting counterpoint.