I suppose the danger of AJ Schnack’s immensely entertaining documentary “Caucus” is that it retells all the hair-raising twists and turns of the 2012 Republican caucus in Iowa as human drama, with the things we’re supposed to care about – the ideology, the “politics” – stripped away. We know for sure that none of these clowns will ever be elected president, so we’re free to view them as flawed, interesting, crazy and sometimes even sympathetic characters in a larger narrative that’s beyond their control. I would argue, in fact, that this gripping and grotesque portrait of retail politics in the...