Just two weeks ago, liberals rejoiced over their strongest election showing in decades — re-electing Barack Obama, picking up seats in Congress and scoring historic state ballot victories that legalized same-sex marriage and recreational marijuana.

But now much of the political left is worried that what seems like a liberal “morning in America” could turn out to be a false dawn.

The focus of their distress is none other than Obama, who many left-leaning Democrats fear will go too far in reaching an accord with Republicans on the “fiscal cliff.” Liberal groups are gearing up media campaigns aimed at pressuring Obama and congressional Democrats to hold the line on proposed GOP cuts to Medicare, Medicaid and other entitlement programs.

One of the first salvos came Tuesday, when a coalition of labor unions announced new television ads demanding that Democrats focus on job creation and not yield to Republican austerity demands. Prominent liberals such as House Minority Leader Nancy Pelosi (Calif.) and Sen. Patty Murray (Wash.) have also signaled that Democrats are prepared to allow automatic spending cuts and tax hikes to take effect if there is no agreement to raise tax rates on the rich.

The moves follow an election night filled with major victories and moments of pure schadenfreude for liberals, such as an on-air meltdown by GOP political mastermind Karl Rove when Fox News called the race for Obama. Democrats have watched with glee as Republicans squabble over the meaning of the election results, including sharp criticism of Mitt Romney and a wide-ranging debate over how to broaden the party’s appeal.

A look at key factors in the 2012 presidential election.

Exit polls showed that 25 percent of voters identified themselves as liberal, up from 22 percent in 2008 and 17 percent in 1984, the year Ronald Reagan was re-elected on his “morning in America” message. Demographic shifts, coupled with Obama’s campaign message of collective responsibility and economic fairness, boosted the resurgence. Some of the nation’s fastest growing groups are also being increasingly drawn to the liberal brand, including Hispanics, college graduates and the non-religious.

“President Obama has arguably created a genuine realignment at the national level that could continue to shape American politics for years to come,” wrote Ruy Teixeira and John Halpin, political scientists at the Center for American Progress, a liberal think tank.

Democrats who once avoided the liberal label also embraced it this year. Forty-six percent of Democrats identified as liberals, up from 39 percent in 2004. Organized labor reaffirmed its power as a ground-level political force, playing a crucial role in delivering Ohio to Obama. Shortly after the election, Pelosi — adored by liberals for her strategic and fundraising prowess —announced that she would stay on as the leader of House Democrats.

Progressives were especially heartened by the results in Maryland, Maine and Washington state, where voters legalized same-sex marriage. In Minnesota, a constitutional amendment defining marriage as exclusively between a man and woman was defeated. Nine states now allow gay marriage; three others recognize same-sex unions performed in other jurisdictions.

Referendums decriminalizing recreational use of marijuana won in Colorado and Washington state. In California, hotbed of the 1970s taxpayer rebellion, voters approved a ballot proposition backed by Gov. Jerry Brown to pump $6 billion a year into K-12 and college education.

For elders of the left, who once listened to Vice President George H.W. Bush attack Massachusetts Gov. Michael Dukakis as “a card-carrying member” of the American Civil Liberties Union in the 1988 presidential campaign, the election and its aftermath were a kind of vindication.

“I always thought the Republican assumption that America is a center-right country was profoundly wrong,” said former labor secretary Robert Reich, now a professor of public policy at the University of California at Berkeley. “People may differ in terms of how large a government they want, and what they want government to do, but we are essentially very tolerant and inclusive.”

But whether a renewed liberal presence will spark a major shift in federal policies is another question. State-level electoral breakthroughs on social issues such as gay marriage and marijuana use don’t clear a path for the liberal economic agenda, leaders and scholars on the left said this week. Core objectives such as narrowing wage inequality, reforming the tax code and ending unlimited money in politics still face daunting obstacles.

“There is a giant disjuncture between the concerns of the working class and the center of gravity for elite Democratic politicians,” said Lawrence Mishel, president of the left-leaning Economic Policy Institute.

A center-left electoral coalition also doesn’t automatically mean a progressive majority in national politics. The same exit polls showing a resurgence in liberal identification also showed that self-identified conservatives edged up slightly to 35 percent of the electorate.

The next Senate will feature a record number of women, including new progressive voices such as Elizabeth Warren of Massachusetts and Tammy Baldwin of Wisconsin. But Democrats will still be short of the 60 votes needed to close off the blocking maneuvers called filibusters.

The House Democratic caucus, while more progressive and with non-white males in the minority for the first time, is still under the thumb of a solid Republican majority.

Teixeira said in an interview that, despite his bullishness on long-term trends, he is “not that optimistic” about the near-term prospects for progressive change. Progressive policies flourish best in times of robust economic growth, he said: “It’s going to be difficult to do if we continue to have a bad economy.”

Others said they saw not a leftward tilt but a corrective maneuver, moving the country to the center after a period of angry anti-government rhetoric and fervor from groups such as the tea party during the 2010 midterms.

American Federation of Teachers President Randi Weingarten, who traveled to 25 states during the 2012 campaign, said what voters really wanted was “a stop to the extremism and the overreaching.”

“If you listen to people, what they’re saying is, ‘Help us reorder our government to create opportunity and jobs,’ ” she said.

The administration has tried to assuage left-wing fears of a cave-in on entitlements. On Wednesday, Obama’s campaign operation sent out a message to supporters saying his focus in the negotiation would be “what’s best for the middle class.”

Last week, Obama also hosted a meeting with 10 key labor and progressive leaders, including AFL-CIO President Richard Trumka, National Education Association head Dennis Van Roekel and Deepak Bhargava, executive director of the Center for Community Change. Bhargava said the group came away confident that Obama remains resolute on rolling back the George W. Bush-era tax cuts for the wealthy.

But other liberals remain deeply skeptical about the ultimate shape of a deal.

“We don’t know where the administration is going to come down on this,” Mishel said. “But there is a reasonable fear that they have a different vision than the people who voted for them.”

Peyton M. Craighill contributed to this report.