This poem tells the story of a song (a song about a snake) from its ancient origins through its incorporation into the soul music of the Sixties to its perversion in the mouth of our president. Trump doesn’t sing the song; instead, at his rallies, he “treats the song like it is a poem,” Juliana Spahr writes, delivering it with a dramatic pause at the end of each line. Of course, Trump gets the origin of the song wrong (“Sometimes he claims it was written / by Al Wilson in the 1990s. / Sometimes he attributes it to Al…