Kabaservice argues that Goldwater’s landslide defeat by the incumbent, Lyndon Johnson (which also helped reduce the number of Republicans in the House to its lowest level in nearly 30 years) actually strengthened the leverage of Republican moderates. In the next few years, liberal Republicans came to the fore, including John Lindsay, who was elected mayor of New York (defeating Buckley, who ran on the Conservative Party ticket); Edward Brooke (of Massachusetts), who became the first popularly elected African-­American senator; George H. W. Bush, who won a House seat in his adopted state of Texas; and Michigan Gov. George Romney (father of Mitt), who briefly posed a serious threat to Richard Nixon’s presidential ambitions — a 1966 Harris poll had him leading the Republican field and defeating Johnson 54-46 — until he blew it all by attributing his initially favorable view of the Vietnam War to “brainwashing” from generals and diplomats. “In hindsight,” Kabaservice pointedly notes, “Romney was the G.O.P. moderates’ last and best chance to elect one of their own to the presidency.”

The Nixon presidency initially seemed a boon for modern Republicans, since Nixon had been Eisenhower’s vice president. His cabinet appointments included moderates like William Rogers, Elliot Richardson, Melvin Laird and Walter Hickel. His national security adviser, Henry Kissinger, a longtime associate of Nelson Rockefeller, was widely deemed a moderate, too. And much of Nixon’s domestic agenda flirted with outright liberalism, particularly the poverty program devised by Daniel Patrick Moynihan, a career Democrat. But Nixon himself was not at heart an Eisenhower Republican so much as a calculating practitioner of realpolitik, and as he increasingly honed his message to appeal to conservative Southern Democrats (aided by his ex-moderate vice president, Spiro Agnew) he grew estranged from moderate Republicans — even as he often pursued liberal policies. Then came Watergate, which alienated moderate donors in the ’70s; direct-mail campaigns for the Republican Ripon Society, an influential liberal group, soon began losing money. At the same time, wealthy conservatives like Joseph Coors, John Olin and the Koch brothers were stepping up their contributions to conservative causes. With the election of Ronald Reagan in 1980, the party lurched farther right, and modern Republicans became scarcer still.

Today, nearly all political centrists are Democrats. And with the rise of the Tea Party, Republicans are experiencing another 1964 moment. Indeed, Theda Skocpol and Vanessa Williamson report in their exceptionally informative book, “The Tea Party and the Remaking of Republican Conservatism,” more than a few Tea Partiers “dated their first political experience to the Goldwater campaign.” But there are important differences between the two movements. For one, the Tea Party, unlike the Goldwater insurgency, has managed to win elections and thereby obtain some power at the national and state level. For another, the Tea Partiers’ anti-­government ideology is tempered by quiet support for Social Security and Medicare. That’s because the activists themselves tend to be middle-aged or older. Tea Partiers aren’t opposed to government benefits per se, according to Skocpol and Williamson; rather, they’re opposed to “unearned” government benefits, which in practice ends up meaning any benefits extended to African-­Americans, Latinos, immigrants (especially undocumented ones) and the young. A poll of South Dakota Tea Party supporters found that 83 percent opposed any Social Security cuts, 78 percent opposed any cuts to Medicare prescription-drug coverage, and 79 percent opposed cuts in Medicare reimbursements to physicians and hospitals. “So much for the notion that Tea Partiers are all little Dick Armeys,” Skocpol and Williamson write. The small government Tea Partiers favor is one where I get mine and most others don’t get much at all.

This poses a particular problem for a conservative Republican like Rep. Paul Ryan, who favors privatizing Medicare and shifting more of the financial burden onto recipients. But it’s also a problem for anyone seeking to lower the budget deficit, because it’s the “earned” benefits like Social Security and Medicare that are mainly responsible for runaway government spending. On the other hand, although Tea Partiers, who tend to be comfortably middle class but not wealthy, hate paying taxes, they don’t necessarily mind when other people pay taxes; the South Dakota poll had 56 percent of Tea Party supporters favoring a 5 percent increase in income taxes for people who earn more than $1 million a year.