Dionne brings some notable qualities to telling this story: E. J. the Brookings scholar knows the academic literature inside out while E. J. the journalist is on first-name terms with many leading conservatives. Dionne is notably fair-minded. Though he makes no bones about his own liberal sympathies, he tries hard to understand the frustrations of white ­working-class voters who have seen their living standards stagnate and their cultural values ridiculed. Unfortunately, the one quality that he does not bring is discipline; his book is much too long and frequently disorganized. Dionne meanders back and forth: Long past the middle of the book he interrupts a discussion of the Tea Party to give an extended history of the rise of the religious right. He never uses one example when he can think of a dozen. He doesn’t just tell us that John McCain reduced his staff from 120 to 50 in July 2007. He insists on crediting this momentous fact in the main text to Dan Balz and Anne Kornblut of The Washington Post. Less would have been more.

Lewis’s knockabout style is a relief after Dionne’s workmanlike prose. He argues that the conservative movement has been captured by “empty-headed talking point reciters, rookie politicians who’ve never managed anything in their lives, media clowns such as Donald Trump, dim bulbs in tight pants or short skirts, professionally outraged shout-fest talking heads and total political neophytes.” He notes that the movement is full of overdogs pretending to be underdogs. Ted Cruz, the Tea Party’s leading champion, was educated at Princeton and Harvard Law School and is married to a Goldman Sachs executive. He accuses these assorted freaks of caring more about stoking outrage than in governing the Republic. The more outrage they provoke the more money they can raise — and the more money they can raise the more outrage they can stoke. But he fails to match stylistic panache with ­intellectual substance.

Some of his argument is familiar. The commentator David Frum in particular has emphasized the way that the party has been captured by self-interested elites. Some of it is self-contradictory: Is the problem that conservatives are amateurs or that they are professionals who are more interested in outrage than good government? And some of it is mistaken: Under the most recent Republican president, know-nothings did much less harm than neoconservatives.

Dionne and Lewis both conclude their books with suggestions on how to fix the right. Dionne argues that conservatives need to recapture the reformist spirit that Dwight Eisenhower embodied: They have to come to terms with the modern world in order to steer it in a more congenial direction. Lewis argues that conservatives must recover the enthusiasm for ideas they had in the Reagan era.

Neither recommendation is particularly convincing (indeed, Dionne almost acknowledges as much in his typically belt-and-braces conclusion). The right has powerful incentives to continue on the same path. The fact that the electorate is smaller and whiter in off-year elections means that the Republican Party has a strong grip on the House of Representatives, and the fact that even a wooden candidate like Mitt Romney came within a few points of winning the 2012 election means that it can justify doubling down on the same old strategy.

Moreover, the forces that are disfiguring the right are likely to spread in future years, consuming the Democrats in much the same way as they have consumed the Republicans. The stagnation of the living standards of average Americans is creating widespread angst. The culture wars are extending to new areas. The ­Internet-enabled news-cum-entertainment industry stokes political resentments even as it creates epistemic anarchy. Interest groups are finding ever more ingenious ways to pretzel the political process. Interesting times don’t remain confined to one part of the political spectrum for very long.