The Carter-Obama comparison is as cliché as it is disconcerting (for Democrats). Carter’s undoing can be cast as rare. Lyndon Johnson would surely have lost in 1968. But he did not run. Carter was the first Democratic president defeated since . . . 1888. Every presidential campaign is a rerun of the past. Just as every re-election campaign is a referendum on the present. In 1888, the Republicans’ previous nominee, James Blaine, aided the current GOP nominee, Benjamin Harrison. Blaine hit hard: “The Democratic Party in power is a standing menace to the prosperity of the country.” Today’s messages are...