The Occupy Wall Street protests spreading across the country are mobilizing liberal activists who have been largely sidelined in the national debate since helping to elect President Obama three years ago.

This should be a relief to the White House, which is eager to excite a Democratic base that has grown disappointed in the president and less excited about reelecting him.

But it is unclear whether this sudden burst of energy on the American left will help Obama and other Democrats. The protests are gaining steam around a set of economic grievances and a wariness of both parties’ reliance on corporate campaign money — and Democratic officials are wondering how, or whether, they can tap into a movement that seems fed up with all brands of partisan politics.

That tension has been evident in recent days in debates raging online and in person at demonstration sites across the country.

An Obama strategist from Florida, Steve Schale, posted on his Facebook page that “clamoring for change is hollow unless you vote.” He linked to an image from the liberal Think Progress blog calling on activists to “Occupy the Polls.”

A former Obama volunteer from central Florida, Madison Paige, retorted on Schale’s page that voting alone couldn’t fix the system, saying, “We have to be willing to do the hardest work — and that means taking a look in the mirror when necessary.”

At Occupy D.C., the McPherson Square encampment inspired by Occupy Wall Street, a shouting match erupted this week when a woman describing herself as a longtime Democratic campaign worker encouraged the young protesters to express their concerns by voting, only to be told that voting wasn’t enough.

Those contentious moments help illustrate the difficulty facing Democratic officials as they try to capitalize on the sudden emergence of liberal energy that is growing fast — but expanding largely separate and apart from traditional party institutions.

Some party allies are trying to help. Unions are providing legal advice, food and Internet service in some locations, with labor leaders intervening late Thursday on behalf of protesters in a dispute with New York City Mayor Michael R. Bloomberg (I) over the use of a Wall Street park.

Party and White House officials are watching mostly from the sidelines.

“We don’t know: Is this a sustaining movement or is it a flash of anger?” said one House Democratic leadership aide, who spoke on condition of anonymity to discuss internal thinking.

John Podesta, who as president of the liberal Center for American Progress is a close White House ally, said the party establishment is waiting to see what happens next. “They’ve opened up an important space for a national conversation, but where it goes from here depends on the staying power of the organizing effort,” he said.

The dilemma mirrors the choice that confronted Republican Party officials in 2009 as the tea party movement found its footing and began challenging establishment figures in the GOP hierarchy. Over time, a series of establishment groups such as FreedomWorks began coordinating with the activists, and the tea-party insurgency began to more closely resemble the energized GOP base.

Liberal activists, though, see the Occupy groups as a potentially more unwieldy phenomenon resistant to traditional politics and skeptical of a party hierarchy criticized from the left as too cozy with Wall Street.

That distrust prompted an awkward moment at an Atlanta demonstration last week, when Rep. John Lewis (D-Ga.), a legendary protester in his own right, was denied the chance to speak. A video of the incident, in which Lewis looked on uncomfortably as activists rose to debate whether allowing a congressman to speak violated the spirit of the protest, became an Internet sensation.

“It’s not a danger — if [Obama] handles it properly,” said Steve Hildebrand, an architect of Obama’s 2008 grass-roots organization who is not affiliated with the reelection effort. “I would encourage him to carefully listen to the people who are passionately protesting Wall Street, big corporations and CEO pay.”

Van Jones, a longtime liberal organizer and former Obama aide, offered a caution as well. Although the protesters may have helped Democrats by “breaking the monopoly” owned by conservatives who prevailed in the 2010 elections and then pushed Washington toward a focus on deficit reduction, he said, Obama has to prove himself to the activists through a more populist approach.

“The fact that Obama has been so close to Wall Street makes this tough going for him,” Jones said.

Jones said the Occupy demonstrations are happening alongside a renewed push by more established groups on the left to operate more independently from the White House.

An early galvanizing moment for the left came over the summer, as hundreds of activists were arrested outside the White House gates to protest the proposed Keystone XL pipeline that would connect Canada’s oil sands to the Gulf Coast. Pipeline opponents are now organizing a Nov. 6 demonstration at the White House and have asked Occupy Wall Street activists to converge on Washington for the event.

Obama and top Democratic officials have so far taken a cautious approach to the demonstrations.

The president said last week that the protesters were “giving voice to a more broad-based frustration about how our financial system works.” But he also defended his past support for bailing out distressed banks after the 2008 financial crisis, saying he “used up a lot of political capital, and I’ve got the dings and bruises to prove it, in order to make sure that we prevented a financial meltdown and that banks stayed afloat.”

Even if Occupy activists do not directly back the president, he can benefit from a national focus on the issues they are trumpeting. Recent polls show that deep anger at Wall Street spans the ideological and partisan spectrum, with a new Washington Post/ABC News survey finding that seven in10 Americans distrust Wall Street financial instutions. That includes 68 percent of independents and 60 percent of Republicans. And Obama aides say they see a fertile target in GOP frontrunner Mitt Romney , a former investment banker who the president’s campaign is likely to try and brand as a product of Wall Street.

Romney, no doubt anticipating the attack, sought to show solidarity with the demonstrators during this week’s GOP candidates debate, saying that “the reason you’re seeing protests . . . is middle-income Americans are having a hard time making ends meet.”

Obama and his campaign, meantime, have promoted the president’s support for new Wall Street regulations and the creation of a consumer protection agency — legislation that most GOP candidates have pledged to repeal. A campaign e-mail urged supporters to pressure the Senate to confirm former Ohio attorney general Richard Cordray to head the new bureau.

The note did not directly mention Occupy Wall Street, but it was distributed last week as the demonstrations gained momentum and seemed designed at least in part to reassure movement sympathizers.

“The goal of this campaign — and this President — is to make sure people who work hard and play by the rules get a fair shake, whether that means being able to get a loan to buy a house and send your kid to college, or not having to go bankrupt when you get sick,” the e-mail said.

Jeremy Varon, a historian at the New School for Social Research in New York City and a liberal activist, described his participation in last week’s Occupy Wall Street march as the most exciting moment in politics for him since Election Night 2008 — and now, he said, liberals are breaking free from Obama.

“I do feel a generation of young progressives has come out of the mystifying shadow of the Obama administration and said to itself, ‘We have values that this presidency isn’t going to advance,’ ” said Varon, 44, a vocal critic of Obama’s anti-terrorism policies.

Several activists camped out in McPherson Square this week expressed a range of feelings about Obama, from indifference to disgust.

Christina McKenna, 26, quit her waitressing job in Richmond and drove to Washington with her 4-year-old twins to remain at the demonstration.

Seated on a blanket in the grass as her son and daughter frolicked nearby, McKenna recalled canvassing and phone-banking for Obama four years ago.

“But I was younger and more naive then,” she said. She said she would not vote for the president this time and doubted he could ever win back her support.

“How good can Obama be when he needs so much Wall Street money?” she asked. “We’re not stupid.”

Staff polling analyst Scott Clement contributed to this report.