Progressive wing waves Elizabeth Warren banner

The movement behind Warren is not as intense as the conservative Tea Party version for Republican candidates, but pushing against the party’s center is the goal for both.

“We’re going to make sure that every Democrat who runs for president is forced to say whether they agree with Elizabeth Warren on key issues, like expanding Social Security benefits and more Wall Street reform,” said Adam Green, the 37-year-old cofounder of the group.

Warren’s impassioned stance on expanding Social Security is in defiance of President Obama’s proposal to trim the growth of benefit payments in future years. On that issue, and for her strident efforts to curb the power of Wall Street’s big banks, she was recently criticized by a centrist think tank as leading the Democratic Party “over the populist cliff.’’

That only further inflamed Warren’s loyal grass-roots allies, with Progressive Change leading the charge last week. Campaign-style signs that the group has created neatly summarize its dedication: “I’m from the Elizabeth Warren wing of the Democratic Party.”

Some Democratic operatives grumble privately about the group’s tactics, but Warren has embraced the group enthusiastically.

She communicates with its leaders regularly about policy and politics, in person or often through one of her top advisors, and has made herself available to the organization’s supporters in conference calls. Last month, she wrote an e-mail sent out on the group’s letterhead, pledging solidarity with its drive to expand Social Security and defending it against an attack from the Washington Post’s editorial page.

Warren declined an interview for this article. Her spokeswoman, Lacey Rose, lauded Progressive Change in a statement that thanked the group for its long-term support, without endorsing all of its methods.

“She shares their belief that there is a growing retirement crisis and that the absolute last thing we should do is cut Social Security rather than make modest changes that would allow us to protect or expand benefits into the future,” Rose said.

Progressive Change and other liberal groups saw a perfect opportunity to mobilize their supporters and generate more publicity for the battle over the party’s direction after Third Way, the centrist Democratic think-tank, leveled its attack on Warren in the Wall Street Journal earlier this month.

Progressive Change leaders sent out press releases and supporter e-mails, and put pressure on Democratic lawmakers affiliated with Third Way to resign from the think tank’s leadership. Warren sent a letter to six major banks asking that they disclose their donations to think tanks.

Senator Jeanne Shaheen of New Hampshire, a Democrat and a cochair of Third Way, said in an e-mail to the Globe that “people on both sides should be careful not to make personal attacks” and that she called Third Way to express displeasure over the “attack on Senator Warren.”

Another group, MoveOn.Org, began airing an ad in Washington on Wednesday calling for an expansion of Social Security. MoveOn said in a press release that it was being aired in response to Third Way’s “attack on Elizabeth Warren.”

The same day, Progressive Change gathered dozens of activists and Social Security recipients in front of Third Way’s offices in Washington’s lobbying district. Members handed over boxes of petitions with 125,000 names “to deliver a rebuke to Wall Street–funded Third Way’s attacks on Social Security and Senator Elizabeth Warren.”

Third Way leaders came out to address the crowd, trying to assure them that they are fellow Democrats who agree on most of the issues, including an expansion of benefits for poor recipients. But in side conversations with activists, their differences were clear, including Third Way’s charge that Progressive Change and other liberal groups rely on selective polling to inflate the popularity of their agenda and avoid making difficult choices to protect the long-term health of Social Security.

“What’s happened in Republican politics is that when people disagree, they’re ejected from the party,” said Matthew Bennett, Third Way’s senior vice president for public affairs. “It would be a very bad thing to happen to Democrats.”

Democratic strategists say there is little evidence that liberal groups including Progressive Change, MoveOn.org, and Democracy for America, founded by Howard Dean, have amassed the kind of power that Tea Party groups have within the Republican Party. But many nonetheless disagree with Progressive Change’s goals.

“To be a national party, we have to have a broad spectrum of political thought within our party,” said Tad Devine, a veteran Democratic strategist.

The group says it wants movement progressives leading key congressional committees and running the White House, people who will be the first out of the gate on policy proposals and who will work strategically with advocacy groups to push policy goals by combining outside pressure with inside legislation.

The group has also challenged at least one Democratic incumbent in a contested primary and attacked fellow liberals, including Obama.

During the 2009 health care debate, the group placed Internet ads and urged its members to call on Senator Bernie Sanders, a Vermont independent and one of the most liberal members of Congress, to fight harder for a public health insurance option.

“He led troops into battle and then there was a perception that he caved prematurely,” Green said.

The group raised $4 million in direct contributions and an additional $2.7 million on behalf of candidates in the 2012 elections. That includes $1.2 million raised for Warren. Its members also placed 574,000 calls to voters on her behalf.

The group, founded in 2009 by former MoveOn.org staffers, has been closely intertwined with Warren’s rise.

In the summer of 2010, Green and 34-year-old cofounder Stephanie Taylor saw an article in Huffington Post warning that the Obama administration might bypass Warren to lead the Consumer Financial Protection Agency. The group gathered about 240,000 signatures, and lots of publicity.

They sat down with Warren a week later at Netroots Nation, an annual conference of thousands of liberal activists, where Warren’s keynote speech made her the weekend’s most sought-after companion.

A year later, before Warren entered the Senate race, the group led efforts to “draft” her into the race, with $100,000 in contributions, hundreds of house parties, and a list of activists gathered from the fight over the consumer agency. A week before Warren declared her candidacy, Green and Taylor sat on her front porch in Cambridge and talked about the nature of power as they sipped iced tea.

They talked about it again in a 30-minute rousing conference call that Warren held with hundreds of Progressive Change supporters, just three days before she defeated Senator Scott Brown.

“Elizabeth Warren is one of us,” Taylor told her fellow activists.