In 2002 John Judis and Ruy Teixeira published a provocative book, The Emerging Democratic Majority, arguing that changing demographic trends in America ultimately favored the Democratic Party. The elections of 2002 and 2004, when Republicans crushed Democrats across the map, blunted that argument and prompted much talk of a permanent Republican majority instead. But Democratic victories in 2006 and 2008, most notably Barack Obama’s campaign, seemed to validate the Judis/Texeira thesis.

A new progressive America is on the rise,” Teixeira, a senior fellow at the Center for American Progress, wrote in a detailed report after the ‘08 election, pointing to Obama’s gains among fast-growing minority groups, the Millennial Generation, better-educated voters, and urban and suburban professionals in purple America. Obama’s election was no fluke, Teixeira argued, but the reflection of sweeping demographic changes that Democrats were well-positioned to capitalize on.

Yet that theory was once again challenged in 2009 and early 2010, as Republicans won major gubenatorial and Senate elections in three states—Virginia, New Jersey and Massachusetts—that Obama won handily. In these elections, Obama’s “coalition of the ascendant” either failed to turn out in sufficient numbers or key blocs, like independent voters and younger professionals, defected to the GOP. Democratic incumbents are now vulnerable across the map in 2010. But Texeira is less panicked than most Democrats in Washington. Long-term demographic and geographic trends continue to benefit the Democrats, he argues in an illuminating new report, “Demographic Change and the Future of the Parties,” released this month. “The Democratic Party will become even more dominated by the emerging constituencies that gave Barack Obama his historic 2008 election, while the Republican Party will be forced to move toward to center to compete for these constituencies,” Teixeira predicts.

Republicans shouldn’t get too cocky, he warns, and would be well-advised to hold off on popping the Champagne. “The Republican Party as currently constituted is in need of serious and substantial changes in approach,” Teixeira writes. Republicans will need to move to the center on social issues and develop sensible conservative solutions to pressing problems, as opposed to just railing against taxes and criticizing everything Obama does, if they want to make inroads with Millennials, Hispanics and college-educated professionals in urban and suburban America—the coalition of the future. "‘The party of no’ has a limited shelf life,” he writes. “That strategy might help make significant gains in 2010, but it will not be enough to restore it to majority status.”

But Democrats, beset by internal dysfunction and legislative gridlock, also run the risk of throwing their majority away. “Their chief challenge now is governance, which is daunting in its own right,” Teixeira writes. “They have an ambitious agenda in areas such as health care, financial reform, education, energy, and global relations that they are having some success in pursuing. If these policies have their intended effects and make serious progress toward remedying problems in these areas, Democrats will be in very good shape indeed and will solidify their support among emerging demographics while destabilizing what is left of the GOP coalition.

Conversely, if the Democrats fail to produce—whether through ineffective programs, fiscal meltdown, or both—even an unreformed GOP will remain very competitive despite the many demographic changes that are disadvantaging the party. The next few years will tell the tale.