Running for president in 1964, Barry Goldwater unveiled a slogan designed to neutralize media accusations of “extremism.” The campaign’s handiwork, “In your heart, you know he’s right,” may well have worked had it not been for the efforts of an anonymous genius at the DNC. Soon enough, Democratic ads began retorting with a line as zingy and memorable as Goldwater’s was earnest and dull. “In your guts, you know he’s nuts” may not have won Lyndon Johnson the election single-handedly, but it found its mark. Govern in prose, campaign in poetry. Rhyme has long been a feature of American political advertising, a tribute to the creativity of campaign operatives and the richness of the English language. While every schoolchild has heard of the 1840 Whig anthem “Tippecanoe and Tyler Too” (composed by a Zanesville, Ohio,...