This is the Democratic Party's moment, its power now greater than any time since the mid-1960s. But do not expect smooth sailing. The party is a fractious group divided by competing interests, factions and constituencies that could explode into a civil war, especially when it comes to energy and the environment.

Broadly speaking, there is a long-standing conflict inside the Democratic Party between gentry liberals and populists. This division is not the same as in the 1960s, when the major conflicts revolved around culture and race as well as on foreign policy. Today the emerging fault-lines follow mostly regional, geographical and, most importantly, class differences.

Gentry liberals cluster largely in cities, wealthy suburbs and college towns. They include disproportionately those with graduate educations and people living on the coasts. Populists tend to be located more in middle- and working-class suburbs, the Great Plains and industrial Midwest. They include a wider spectrum of Americans, including many whose political views are somewhat changeable and less subject to ideological rigor.

In the post-World War II era, the gentry's model candidate was a man such as Adlai Stevenson, the Democratic presidential nominee who lost twice to Dwight D. Eisenhower. Stevenson was a svelte intellectual who, like Barack Obama, was backed by the brute power of the Chicago machine. After Stevenson, the gentry supported candidates such as John Kennedy – who did appeal to Catholic working class voters – but also men with limited appeal outside the gentry class, including Eugene McCarthy, George McGovern, Gary Hart, Bill Bradley, Paul Tsongas and John Kerry.

Hubert Humphrey, a populist heir to the lunch-pail liberalism of Harry Truman (and who was despised by gentry intellectuals) missed the presidency by a hair in 1968. But populists in the party later backed lackluster candidates such as Walter Mondale and Dick Gephardt.

Bill Clinton revived the lunch-pail Democratic tradition; and the final stages of last year's presidential primaries represented yet another classic gentry versus populist conflict. Hillary Clinton could not match Barack Obama's appeal to the gentry. Driven to desperation, she ended up running a spirited populist campaign.

Although peace now reigns between the Clintons and the new president, the broader gentry-populist split seems certain to fester at both the congressional and local levels – and President Obama will be hard-pressed to negotiate this divide. Gentry liberals are very "progressive" when it comes to issues such as affirmative action, gay rights, the environment and energy policy, but are not generally well disposed to protectionism or auto-industry bailouts, which appeal to populists. Populists, meanwhile, hated the initial bailout of Wall Street – despite its endorsement by Mr. Obama and the congressional leadership.

Geography is clearly a determining factor here. Standout antifinancial bailout senators included Sens. Byron Dorgan of North Dakota, Tim Johnson of South Dakota, and Jon Tester of Montana. On the House side, the antibailout faction came largely from places like the Great Plains and Appalachia, as well as from the suburbs and exurbs, including places like Arizona and interior California.

Gentry liberals, despite occasional tut-tutting, fell lockstep for the bailout. Not one Northeastern or California Democratic senator opposed it. In the House, "progressives" such as Nancy Pelosi and Barney Frank who supported the financial bailout represent districts with a large concentration of affluent liberals, venture capitalists and other financial interests for whom the bailout was very much a matter of preserving accumulated (and often inherited) wealth.

Energy and the environment are potentially even more explosive issues. Gentry politicians tend to favor developing only alternative fuels and oppose expanding coal, oil or nuclear energy. Populists represent areas, such as the Great Lakes region, where manufacturing still plays a critical role and remains heavily dependent on coal-based electricity. They also tend to have ties to economies, such as in the Great Plains, Appalachia and the Intermountain West, where smacking down all new fossil-fuel production threatens lots of jobs – and where a single-minded focus on alternative fuels may drive up total energy costs on the farm, make life miserable again for truckers, and put American industrial firms at even greater disadvantage against foreign competitors.

In the coming years, Mr. Obama's "green agenda" may be a key fault line. Unlike his notably mainstream appointments in foreign policy and economics, he's tilted fairly far afield on the environment with individuals such as John Holdren, a longtime acolyte of the discredited neo-Malthusian Paul Ehrlich, and Carol Browner, who was Bill Clinton's hard-line EPA administrator.

These appointments could presage an environmental jihad throughout the regulatory apparat. Early examples could mean such things as strict restrictions on greenhouse gases, including bans on new drilling and higher prices through carbon taxes or a cap-and-trade regime.

Another critical front, not well understood by the public, could develop on land use – with the adoption of policies that favor dense cities over suburbs and small towns. This trend can be observed most obviously in California, but also in states such as Oregon where suburban growth has long been frowned upon. Emboldened greens in government could use their new power to drive infrastructure spending away from badly needed projects such as new roads, bridges and port facilities, and toward projects such as light rail lines. These lines are sometimes useful, but largely impractical outside a few heavily traveled urban corridors. Essentially it means a transfer of subsidies from those who must drive cars to the relative handful for whom mass transit remains a viable alternative.

Priorities such as these may win plaudits in urban enclaves in New York, Boston and San Francisco – bastions of the gentry class and of under-35, childless professionals – but they might not be so widely appreciated in the car- and truck-driving Great Plains and the vast suburban archipelago, where half the nation's population lives.

If he wishes to enhance his power and keep the Democrats together, Mr. Obama will have to figure out how to placate both his gentry base and those Democrats who still see their party's mission in terms that Harry Truman would have understood.

This article originally appeared at Wall Street Journal.

Joel Kotkin is executive editor of NewGeography.com and is a presidential fellow in urban futures at Chapman University. He is author of The City: A Global History and is finishing a book on the American future.