The Candidate: What It Takes to Win—and Hold—the White House by Samuel L. Popkin Oxford University Press, 350 pp., $27.95

For many years, specialists in universities believed that American political events could be explained by the methods of economics and political science. The recent lackluster jobs report, for example, showing just 120,000 private-sector jobs added in March, is precisely the sort of fact that these experts would find explanatory. They assumed that party politics didn’t really matter that much—that when it came, for example, to making decisions about economic policy, politicians of both parties, though they would disagree on some fundamental questions, acted rationally, listening to the views of their respective economic experts and attempting to carry out their recommendations in as much good faith as the sausage-making processes of party politics would allow.

It took them a while, but that view has begun to change. Now, the components of politics—everything from ideology to the influence of money to overbearing egos and hostile personal relations, all the matters that have for decades consumed the political press but been of less interest to the academy—are understood to drive the action. Or at least acknowledged as factors. The influential books along these lines include Jacob Hacker and Paul Pierson’s Off Center of 2005, in which the writers—political scientists—described the process by which a comparatively small and radical Republican group of lawmakers and their benefactors had moved the country so far to the right. Two years later, in The Conscience of a Liberal, Paul Krugman admitted that he’d been wrong all these years in putting economic explanations before political ones. Considering inequality, for example, he wrote that he’d been coming to conclude that mere economic explanations for it no longer sufficed:

Can the political environment really be that decisive in determining economic inequality? It sounds like economic heresy, but a growing body of economic research suggests that it can.

The year after that brought publication of the political scientist Larry Bartels’s Unequal Democracy. Bartels, now at Vanderbilt, then at Princeton, was, like Krugman, concerned in the first instance with our growing (not to say rampaging) economic inequality. He didn’t want to believe that a factor as pedestrian as which party the president belonged to could really matter in determining inequality. But after studying the evidence and finding that inequality had tended to increase dramatically under Republican presidents and decrease under Democratic ones going back to Harry Truman’s day, Bartels confessed: “If this is a coincidence, it is a very powerful one.”1

I would add finally to this list the bracing new book Why Nations Fail, by the economists Daron Acemoglu and James Robinson,2 who survey societies from ancient times to medieval Venice to post-1688 England to today’s China, looking to pinpoint the reason why nations rise and fall. The answer, they write, is the creation of economic institutions that permit broad prosperity. But those institutions are created in the first instance by politics, so the real question for Acemoglu and Robinson is whether a…