Growing up in Texas, we were treated to stories of colorful political characters. Few could top John Nance “Cactus Jack” Garner, who once pronounced that the vice-president position “is not worth a bucket of warm spit.” (Some say Garner said worse.) That seems to be the opinion of more than a few pundits and political scientists. National Public Radio, The Economist and Politico have all run articles asserting how little impact a vice presidential pick makes on the ultimate outcome of a presidential election. I take a different approach, comparing vice presidential picks’ performance in their …