Sean Wilentz is a contributing editor at The New Republic, and the author of Bob Dylan in America (Doubleday). This excerpt is drawn from a longer review of Robert Caro's Passage to Power.

...BARACK OBAMA came to the presidency with enormous gifts but only four years of indifferent government experience in Washington, which partly accounted for his perception of recent political history and the crisis he faced, above all his notion of the Republican Party. Since the departure of Ronald Reagan, the Republicans on Capitol Hill, and especially the House, had lurched fitfully further to the right, their caucus centered in the white conservative South that Johnson and the Democrats had abandoned when they fought for civil rights and which Goldwater first gathered up for the GOP. Like the conservative counter-revolution of 1938 and after, this had been the overriding reality of congressional politics after 1994.

Following the defeat of President Bill Clinton’s health care reform early in his first term, the Republicans regained the House majority led by the right-wing agitator Newt Gingrich; and after Clinton recovered to outfox Gingrich and then win re-election, the Republicans pushed ever further to the right, under the command of House Majority Leader Tom DeLay, who commandeered the impeachment farce and then forced Gingrich out. The conservative five-to-four majority on the Supreme Court placed George W. Bush in the White House, but Bush’s “compassionate conservatism” quickly gave way to the brutal and politicized methods of Dick Cheney and Karl Rove. The DeLay-led right-wing Republican Congress was happy to go along, even after DeLay’s money-laundering corruption came to light, after which the Democrats regained the House majority in 2006. By then, most of the country had turned fiercely against Bush—and so would the irreducible hard-right base over his desperate effort to stanch the worst financial crisis since the Great Depression with a massive bailout of financial institutions. This right-wing revulsion against Bush as a secret “big-government” betrayer would in time explode as the Tea Party.

Looking back on this history, the impeccably centrist political scientists Norman J. Ornstein and Thomas E. Mann have recently observed that the undeniable reality for decades—obscured by a cowed press corps intent on proving its objectivity—is that right-wing Republicans, especially in Congress, have been the cause of the intensified polarization in Washington, turning their party into “an insurgent outlier in American politics.” Yet in the face of this reality, Obama propagated the idea that both parties were responsible for the acidulous politics of the 1990s, that “politics as usual” and “the old Washington games with the same old Washington players” had produced stalemate. He offered instead a transcendent and “transformative” post-partisanship that would carry the country to the higher ground of peace, prosperity, and social justice. He would be the latest antidote to the kind of low political scheming that an earlier generation of reform Democrats had seen and detested in Lyndon Johnson and, in many cases, in Robert Kennedy as well.

Obama came into office in 2009 with a more favorable political situation than Johnson faced in 1963 and 1964. To be sure, Kennedy’s martyrdom gave Johnson enormous public sympathy, which he was unashamed about exploiting politically. And by the time Obama became president, the sort of right-wing revanchism and even paranoia that in Johnson’s day occupied the margins of American politics, in groups such as the John Birch Society, had become part of the mainstream inside the Republican Party as well as on cable television and the Internet. But unlike the longentrenched bipartisan conservative majority that Johnson confronted, Obama faced a fractured opposition party that was in public disgrace after the eight-year Bush regime and whose candidate, Senator John McCain, had just conducted the feeblest presidential campaign since the Michael Dukakis campaign in 1988. (Even Dukakis had not given America an indignity on the order of Sarah Palin.)

Johnson was an accidental president who had run on a ticket that barely squeaked by three years earlier; Obama had been elected to office with the first presidential popular majority that his party had enjoyed in more than thirty years and the largest in more than forty. On Inauguration Day, Obama enjoyed an astounding 69 percent public approval rating. More important, he enjoyed a seventy-nine-seat Democratic majority in the House and a filibuster-proof ten-seat Democratic majority in the Senate—in short, a working party majority, unlike the Southern-Midwestern conservative axis that Johnson confronted. Johnson, by contrast, began his presidency in political loneliness, detested by Kennedy liberals, alienated from Southern Democrats, and mistrusted by Republicans. And out of this isolation he produced a genuinely transformative presidency....