Elizabeth Warren just fired the opening shot in the budding Democratic civil war

It was shortly after 1:30 p.m. on Thursday when the Democratic dam broke, a long-brewing feud spilling out into the open.

House Minority Leader Nancy Pelosi, one of President Barack Obama’s staunchest defenders, stood on the floor and publicly denounced the White House in the fight over a must-pass spending bill to keep the government from shutting down.

“I’m enormously disappointed that the White House feels that the only way they can get a bill is to go along with this, and that would be the only reason they would sign such a bill that would weaken a critical component of financial system reform aimed at reducing taxpayer risk,” Pelosi said.

For this battle, Pelosi, a 27-year veteran of Democratic politics, found herself a foot soldier in a new—and rising—wing of the party: the “Warren Wing,” named after Sen. Elizabeth Warren, the ascendant senior senator from Massachusetts.

Warren had come out forcefully against the spending bill when it became clear that Republicans had tucked into the bill a provision that rolls back part of the landmark 2010 Dodd-Frank financial reform law. She prompted a growing number of Democrats, including Pelosi, to revolt against the bill, nearly derailing it before the White House began urging on-the-fence Democrats to support for the bill later Thursday afternoon.

It’s only the beginning for Warren and her growing faction in the Democratic Party, as she has increasingly emboldened the populist, anti-Wall Street wing of the party over the side that has closer ties to Wall Street. Her most vocal supporters say she represents where the party is heading in the future. But skeptics point to what has so far been limited broad appeal beyond self-identified progressives — last month, CNN poll found her trailing Clinton 65-10 among Democrats.

Either way, Thursday’s events may be a sign of things to come in the last two years of Obama’s presidency—and on the campaign trail in 2016.

“We believe that this year could well see the public emergence of the Democrats’ version of the Tea Party,” said Chris Krueger, a Washington analyst at Guggenheim Securities, an investment advisory and financial services firm. “Four years of a media focus on the drift of the GOP towards a more conservative bent have missed a major structural shift in the Democratic Party.”

“The Democratic Party’s economic message,” he added, “has shifted from the Bill Clinton-Robert Rubin axis towards a more aggressive populism and anti-corporate message.”

That will present an interesting dynamic in the next two years for a party whose presumptive frontrunner bears the last name Clinton.

There’s perhaps no clearer indication of the growing divide in Democratic politics than in the example of former presidential candidate and Vermont Gov. Howard Dean, who has found himself in direct contrast with the liberal organization he founded.

On Wednesday, Dean came out and endorsed Clinton in a Politico op-ed, making the “liberal case” for supporting Clinton. At the crux of his argument is that Clinton understands the frustrations of liberals over the recent rightward shift of the Supreme Court, and she’ll have the chance to potentially appoint one or more justices during her theoretical presidency to balance it out. But Dean also wrote he expects Clinton to step up to a key challenge Democrats want to see their candidate take head-on — income inequality.

His endorsement puts him at odds with Democracy for America, the organization he co-founded in 2004 and for which he remains a senior adviser. On Tuesday, Democracy for America joined fellow left-leaning group MoveOn.org in announcing they would attempt to push Warren to run in 2016 and challenge Clinton.

MoveOn will invest at least $1 million in pressuring Warren to run after more than 80 percent of its members voted for the move. The campaign will include public events, field offices in key early presidential states like Iowa and New Hampshire, and cutting of videos and ads promoting Warren’s potential candidacy.

“We are at a crucial time in our nation’s history, with income inequality higher than it’s been since the 1920s and with a playing field increasingly skewed in favor of Wall Street banks and corporate lobbyists,” said Ilya Sheyman, the executive director of MoveOn Political Action. “Senator Warren’s fearlessness in standing up to corporate interests and fighting for the middle class and working families is exactly what we need in the presidential race.”

Neil Sroka, the communications director of Democracy for America, said it’s simple — the No. 1 issue for Democrats in 2016 will be income inequality. And on that point, Warren is “by far the most articulate leader our party has.”

Sroka said the party is quickly separating into two partitions — the “Warren wing” and the “Wall Street wing.” The White House’s public push on Democrats to support the bill represented only the most recent example in liberals’ growing frustration with the Obama administration.

“Whenever I hear the White House is heading down to Capitol Hill, I get increasingly worried about the legislation,” Sroka told Fusion, referring to White House chief of staff Denis McDonough’s trip to meet with House Democrats late Thursday evening.

Warren’s entry into the government-funding battle was the second time in two weeks she has taken direct aim at the White House. She also has waged a public campaign against Antonio Weiss, who Obama has nominated to fill the post of treasury undersecretary for domestic finance.

Weiss is a prominent Democratic donor, having given huge sums of money to various state parties, to Democratic Sens. Mark Warner (D-Virginia), Cory Booker (D-New Jersey), and Chuck Schumer (D-New York), and to Obama’s re-election campaign. Warren has attacked his ties to Wall Street and the fact that he worked overseas for much of his career in the banking sector, ruffling feathers in and outside of the White House.

Warren has already gotten results, and Obama will need help from Republicans to get Weiss appointed to the position. Sen. Richard Durbin (D-Illinois), the No. 2 Senate Democrat, is opposing Weiss, as are Democratic Sens. Joe Manchin (D-West Virginia), Jeanne Shaheen (D-New Hampshire), and Al Franken (D-Minnesota).

Some Democratic leaders think Warren, who will enter Senate Democratic leadership at the start of next Congress, has been shrewd in approaching her increasingly public role. One Senate Democratic leadership aide, who requested anonymity to speak frankly, said she had been effective in the funding battle by picking the right “pressure point.”

“She was also skillful in finding a pressure point in the legislative process that she used to elevate the cause,” the aide told Fusion. “In the end, no one wanted a government shutdown – including her – but she accomplished the mission of setting the Democrats on a path of fighting for the 99 percent.”

Other prospective candidates are starting to take notice. Outgoing Maryland Gov. Martin O’Malley, who is mulling a run, criticized the Dodd-Frank provision in the spending bill on Friday. Sen. Bernie Sanders, an Independent from Vermont who caucuses with Democrats and may be the most liberal Democratic candidate in 2016, said he would oppose the bill because it comes “nowhere close to reflecting the needs and priorities” of middle-class families.

But the true wild card in the presidential race could be Warren, though she has continually denied she has any interest in a run. That hasn’t stopped groups like MoveOn and Democracy for America from trying. And on Friday, more than 300 former Obama for America staffers released an open letter urging her to run.

“The lesson that Democrats should’ve learned from the 2014 election is that the Wall Street wing of the party is dead and dying,” Sroka told Fusion. “And the Warren wing is rising.”

Brett LoGiurato is the senior national political correspondent at Fusion, where he covers all things 2016. He’ll give you everything you need to know about politics, with a healthy side of puns.