NEW YORK (AP) - As she campaigned through Iowa this week, Sen. Elizabeth Warren of Massachusetts didn't hesitate to jab the newest contender in the 2020 Democratic presidential primary: Joe Biden.
"Our disagreement is a matter of public record," Warren said, referring to Biden's past support of a massive bankruptcy overhaul. "Joe Biden was on the side of the credit card companies."
The early days of the 2020 Democratic primary have been defined by order, amicable disagreement and an overwhelming focus on defeating President Donald Trump.
Biden's campaign launch on Thursday ushered in a new phase in the nominating contest. With the field largely set, the leading candidates have begun to turn on one another, raising the prospect of an ugly fight for the future of the party that could have lasting consequences for Democrats' quest to reclaim the White House.
Progressive groups aligned with Warren and Sen. Bernie Sanders of Vermont took aim at Biden, portraying him as out of step with today's Democratic Party. They railed against his connections to big corporations, his past support for a "grand bargain" that would have cut Social Security and Medicare, and his support for a 1994 crime bill that disproportionately hurt minorities.
"For numerous reasons, Joe Biden is the least electable Democrat that we could possibly nominate," said Adam Green, co-founder of the liberal group known as the Progressive Change Campaign Committee, which has long supported Warren's presidential ambitions. "We're in a new moment. This is not Joe Biden's moment."
Sanders' campaign manager slapped at the former vice president in a fundraising message titled "Joe Biden."
"Not only are we taking on a political and corporate establishment that will do and spend whatever it takes to stop us, but we are running against a record number of candidates at the same time," Faiz Shakir wrote. He added: "There are a lot of candidates in this race right now. But there is only one Bernie Sanders."
Biden's campaign said Friday it raised $6.3 million in the first 24 hours since announcing, narrowly besting Sanders' first-day haul.
Desperate to deny Trump a second term, Democrats can ill afford any lasting divisions that could depress turnout come November 2020.
The early infighting has already caught the attention of party leaders like Democratic National Committee member Robert Zimmerman, of New York, who helped raise money for former President Barack Obama and Biden in years past.
"The No. 1 issue that I've seen across the country is Democrats staying focused on beating Donald Trump. I demand that Democrats remain positive with each other," Zimmerman said. "Any Democrat who tries to build their message by maligning or attacking personally their opponent is going to disqualify themselves."
Yet the battle lines are quickly hardening. With emboldened liberals on one side, pro-Biden establishment leaders in Congress and labor unions are lining up on the other.
Biden, who served in the Senate for nearly four decades, won immediate endorsements from Sen. Bob Casey of Pennsylvania, Sen. Chris Coons of Delaware and Sen. Doug Jones of Alabama, while Sen. Dianne Feinstein of California had already declared her support. None of the other 2020 contenders has the endorsement of more than one U.S. senator.
The largest firefighters union in the country, the International Association of Firefighters, was also preparing to endorse Biden. Group leaders have said they would be "investing" heavily in his campaign.
Biden himself took an indirect swipe at his Democratic competitors earlier in the month as he defended his liberal bona fides: "The definition of 'progressive' now seems to be changing. And that is, Are you a socialist?'" he said. Sanders, who is Biden's closest competitor in recent polls, describes himself as a democratic socialist.
The establishment support lining up behind Biden could embolden his critics on the left.
Prominent black Democrats seized on the 1994 crime bill, which Biden helped craft and is now blamed for creating an environment of mass incarceration that disproportionately hurt people of color.
"So @JoeBiden you were the author of the 94 Crime Bill, it's champion, and #1 cheerleader," tweeted Bakari Sellers, a former South Carolina state Democratic elected official and prominent African American voice on television. "This bill has led to mass incarceration and specifically targeted black and brown people. What are your plans to unravel the damage you helped to cause?"
Of course, there's time for Biden to win over the critics. Primary voting begins in roughly nine months, and the general election isn't until November 2020.
Some of Biden's liberal attackers indicated they would support him over Trump should Biden win the nomination. In a nod to his opponents, he also hired former Sanders' aide, Symone Sanders, to serve as a senior campaign strategist.
Biden and his wife "are a class act," tweeted Symone Sanders, who isn't related to Bernie Sanders. "Over the course of this campaign, Vice President Biden is going to make his case to the American (people). He won't always be perfect, but I believe he will get it right."
Associated Press writer Alexandra Jaffe in Des Moines, Iowa, contributed to this report.