Many Democrats and liberal-progressive pundits are obsessed these days with the idea that they are being robbed of victories by the structure of the American electoral process. One element of this complaint is the charge that the Republican dominance of the House of Representatives is due to partisan gerrymandering. Former attorney general Eric Holder has pledged to dedicate himself to attacking gerrymandering, and former president Barack Obama has likewise indicated that he will make it a major cause of his post-presidency, the most directly partisan focus of any former president in living memory. A November court decision striking down Wisconsin’s …