Across the last half-century or so, Doonesbury has been one of those rare institutions that could always be counted on—even while the political world it described seemed to be run by people who couldn’t be counted on at all. Whether it was following the daily trials and pleasures of the lovelorn, the divorced, the dying, the homeless, the enlisted, or those Zonker-like individuals who felt estranged from the whole ugly process that calls itself …