Long live the Democrats? Not so fast.

With the election of President Obama and a Democratic Congress, some liberals tout the dawn of a permanent Democratic majority.

Republican strategist Mike Murphy, writing in this week's Time magazine, warned Republicans that their "ice age cometh." Demographic changes, Mr. Murphy argued, particularly increases in Latino and young voters, heavily favor Democrats. It's an argument that has been popular in Democratic camps for a while now.

But as Karl Rove learned, no majority is permanent. And political majorities are built, not born. Demographic changes alone won't be enough to continue winning elections. For that, Democrats must sell the idea of benevolent government and capture the language of populism that has been the exclusive provenance of Republicans for nearly 40 years.

Winning the ideological argument that government can be a force of goodwill helps the Democrats do more than just win elections. It will enable them to pass the programs and policies the left sees as the foundation of a better America.

After all, Democratic President Bill Clinton won two terms, but he did so while declaring that "The era of big government is over." His failure to win the argument over the value of government action helped Mr. Clinton lose the healthcare battle and led him to claim free-trade legislation and welfare reform as the major victories of his administration.

Democrats have returned to power in an era more receptive to government programs. The reigning issue of the day, the financial crisis, can be traced to Republican-era deregulation. Healthcare remains a pressing concern, one a majority of Americans believe will require government intervention to solve.

Yet at the same time, last week's Gallup poll showed 40 percent of Americans identify themselves as conservative, while only 21 percent identify themselves as liberal. Not all of that 40 percent are movement conservatives. And plenty of progressives shudder at the liberal label. But the poll does suggest that while the Republican Party may lag far behind the Democrats in party identification numbers – 22 percent to 39 percent, respectively, in an April Pew Research Center poll – there is still hefty resistance to substantial political change.

Aware theirs is not a lost cause, Republicans have been gearing up for a fight over "good government." Witness the right's recent fascination with the American Progressive movement of the late 19th century, 20th century. The first to successfully articulate the need for an active federal government to protect Americans from social ills, the Progressives (as distinct from the small-p progressives today) were the progenitors of 20th-century liberalism. They won Americans the first consumer rights (the Pure Food and Drug Act), the first labor rights (the abolition of child labor), and some of the first significant economic regulations (the Sherman Anti-Trust Act and the Federal Reserve). All told, a powerful example for today's Democratic Party.

The latest missives on Progressives by American conservatives, however, give a much different view of these early government reformers.

Jonah Goldberg, now editor at large for National Review Online, took on the Progressives in his 2008 book, "Liberal Fascism." As its title implies, the book disdains early Progressives as racist, fascist warmongers – the end result, Mr. Goldberg suggests, of the liberal worldview. In the upcoming issue of his magazine Fusion, conservative talk-show host Glenn Beck pits the Progressives against the Founders to argue how un-American the Progressive philosophy was.

True, the early Progressives had their problems. They were paternalists, not populists, and had little faith in mass democracy. But they also believed government could be a force of good in people's lives, and much of their legislation remains central to American life, from land conservation to workers' safety to the nonpartisan agencies at the heart of modern governance.

For Democrats to build a sustainable majority, they will have to take a page from the Progressive playbook – with one important modification. The Progressives believed in a technocratic state, run by experts and protected from the whims of the masses. That won't fly in today's America.

For Democrats to sell the idea of benevolent government, they must combine it with the language and spirit of populism. Twenty-first-century government cannot just be government for the people, as it was for the Progressives at the height of their movement. It has to be government by the people. Such populism must go beyond the voting booth. The agencies that set the rules for governing are not subject to elections, and often the needs of citizens come second to the needs of industries and politicians. To inject the voice of the people into the day-to-day work of governing, citizens' groups must have a prominent and permanent place in the programs and agencies Democrats create.

The Democratic Party must also wrest populist rhetoric from conservatives. Mr. Obama understood this in his campaign, and despite attempts by opponents to paint him as an elitist, Obama emerged as the leader of a grass-roots movement.

For a lasting Democratic majority, the party must embrace the populism of the Obama campaign and show the American people how the party's platform places people above partisanship and special interests.

If they succeed, the Democrats will not secure a permanent majority, but they will build an effective and enduring one.

Nicole Hemmer is a former fellow at the Miller Center of Public Affairs and a PhD candidate in history at Columbia University in New York. She is writing a history of conservative media.