From the 1830s to the 1930s, most presidential elections were shaped by the major parties rather than by charismatic candidates or overriding issues. The great exception was the clash in the 1850s over slavery, states’ rights, and the territories, which divided the Democrats and destroyed the Whigs. But the Republicans quickly replaced the Whigs, and two-party hegemony prevailed thereafter.

Since the 1930s, a new kind of political environment, in which the candidate’s appeal to particular groups coexists with the lure of party identity, has come into being. Franklin D. Roosevelt’s New Deal seems to have been the first American political movement to which the term “coalition” was applied. True, FDR heavily relied on the traditional Democratic party of the rural Protestant South and the urban-immigrant North. But by 1936 he had added groups not previously conspicuous for their Democratic fealty: African-Americans most dramatically; organized labor; Jews.

Political coalitions shaped by foreign and domestic developments rather than the traditional pull of party loyalty and regional or ethnic identity are a recurring feature of modern American politics. In the 1950s Dwight D. Eisenhower attracted not only traditional Republicans, but Catholics and new suburbanites, many of whom had been part of the New Deal coalition. Postwar prosperity, the Cold War, and Ike’s personal appeal had a destabilizing political impact comparable to the Great Depression and the rise of FDR. Lyndon B. Johnson in 1964 was supported by affluent professionals traditionally labeled Country Club Republicans. Ronald Reagan in the 1980s won classically New Deal Democratic working class voters.

Issue politics frequently wreaks havoc with traditional party loyalties. The third party candidacies of Strom Thurmond and Henry Wallace in 1948, of George Wallace in 1968, and of Ross Perot in 1992 and 1996, attracted substantial numbers of voters. Ideological takeovers within the major parties--by Republican Barry Goldwater in 1964, by Democrat George McGovern in 1972--dramatically revealed the destabilizing political impact of the Cold War, the civil rights movement, the Vietnam war, and the cultural upheaval of the 1960s and 1970s.

With the rise of Barack Obama, coalition-identity politics has taken a new, but in this context not unfamiliar, turn. Three social groups are at the core of the Obama coalition (or, as he often calls it, the “movement”): African-Americans, the college/post-college young, and affluent “progressive” Baby Boomers who came of age in the 1960s.

Black Americans have been voting Democratic for decades, by percentages in the 80s. Obama (despite his untypical background and upbringing) represents that group’s political coming-of-age. His powerful attraction to African-Americans is as understandable as Al Smith’s appeal to Catholics and other immigrants in 1928.

Obama’s age, looks, eloquence, and postmodern cool make him attractive as well to the college-educated young. Here the historical analogue shifts: to John F. Kennedy. Obama’s mix of an unthreatening black persona and academic patina echoes JFK’s blend of Irish Catholic political smarts and Harvard polish.

Boomer liberals, clustered in the media, the academy, law, the entertainment industry, information technology, and financial marketing, have long been starved for a cause, and a sense of political community, of the sort that prevailed in the glory days of the struggles over Vietnam and civil rights. They yearn for a spokesperson who embodies the new, diverse, post-racist America, and the political “progressivism” with which they identify. Obama’s persona combines a deliciously exotic family background (black and white, Christian and Muslim, American, African, and Asian) with his exceptional poise, personality, intelligence, and rhetorical skill. And he has an unimpeachably left-liberal political record. He taps Boomer aspirations with an appeal unmatched since the Kennedys.

Past coalitions were fed by big issues: the Great Depression, the Cold War, civil rights, Vietnam. What stokes the Obama movement? The Iraq war is a contributing factor, but in its scale it is no Korea or Vietnam. And Obama appeals eloquently to widespread public discontent over the state of the nation. Yet that discontent extends not only to Bush’s presidency and the Iraq war, but to the Democratic Congress, the media, big business, and universities, from not all of which Obama dissociates himself.

The dominant note of Obama’s campaign has been his pledge to bring a sundered nation together, to transcend the bitter partisanship of the recent past. Yet his Senate record and his pre-Senate career is of all but unalloyed support for left-liberal Democratic policies. A fair reading of his campaign message is that he seeks independents and Republicans who support his policies, not that he will adjust his views to theirs. In this sense he is something of a stealth candidate, recognized as a man of the Left by the cognoscenti but (unlike Goldwater or McGovern) presenting himself to the electorate as a post-ideological politician.

Neither Iraq, nor global warming, nor the economy have had the centrality in the Obama campaign that might have been expected. His success to date appears to be due primarily to his oratorical power and the freshness of his political personality, as well as a brilliant, well-funded campaign. His mantras of “Hope” and “Change”--even “Change You Can Believe In”--echo the vagueness of the Perot campaigns of 1992 and 1996, and in this sense resonate with the call to arms of the 1976 movie Network: “I’m as mad as hell, and I’m not gonna take it anymore!”

But perhaps that is the essence of Obama’s attraction: not programmatic change, but a political style whose very unspecificity allows his constituencies to read into it their diverse hopes and desires.

Is this enough? Can he reach out beyond his core support to attract the additional voting public necessary for electoral victory and effective governance? Does his coalition have the political potential of FDR’s New Deal, or Ike’s modern Republicanism, or Reagan conservatism? Or is it fated to flame out (though perhaps leaving an ideological and organizational legacy), as did the Goldwater and McGovern movements?

That will depend on his crafting a fuller political agenda than he has offered, and/or his capacity to govern from the Left. On the latter count, the record since the 1960s is not promising. Many of the Great Society’s social programs were unsuccessful. Carter’s liberal initiatives went nowhere. Clinton’s initial foray into Ted Kennedy-like liberalism (after a JFK-like campaign) crashed and burned in the congressional election of 1994. Whether or not Obama will be able to respond effectively to the current popular disaffection is equally uncertain.

But these are new times with new problems. And much of the electorate and the policy establishment have little or no recollection of the unsatisfactory past. A decisive electoral victory, and sufficiently large congressional majorities, could conceivably enable Obama to craft a legislative and ideological equivalent of the New Deal, and fulfill Jimmy Carter’s aspiration to dispel the malaise that supposedly afflicts the nation.

But I wouldn’t bet on it. Obama has already substantially moved from the anti-Israel stance of his early foreign policy consultants, and has modified his previous get-out-of-Iraq-now position: sources of potential trouble with his ideology-driven supporters on the Left. Nor is it clear yet what the character of a new course in economic or social policy might be. Barring the trauma of depression or war, the staying power of our political system, and the entrenched character of our institutions, are as likely to limit the impact of the Obama coalition as they did its predecessors.