Sens. Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt., both appeared to take shots at former Vice President Joe Biden in his first official day on the campaign trail.
Their remarks offered some of the first intraparty criticism to emerge from the pool of at least 20 Democrats running to defeat President Donald Trump in the 2020 election. When Biden joined the race Thursday, he was widely viewed as an instant front-runner.
On Thursday, Sanders' campaign sent a shot across the bow at Biden in response to a reported fundraiser in Philadelphia on Thursday evening at the home of Comcast Senior Executive Vice President David Cohen. Comcast owns CNBC parent NBCUniversal.
In an email to supporters sent Thursday under the subject line "Joe Biden," the self-described democratic socialist's campaign wrote: "It's a big day in the Democratic primary and we're hoping to end it strong. Not with a fundraiser in the home of a corporate lobbyist, but with an overwhelming number of individual donations."
Warren, meanwhile, dredged up her past criticisms of Biden's record on financial issues during his three decades in the Senate.
"Joe Biden was on the side of credit card companies," Warren said Thursday at an event in Iowa when asked about Biden's relationship to Wall Street, according to The New York Times.
Her disagreement with Biden over bankruptcy legislation "is a matter of public record," she said.
Indeed, Warren targeted Biden in her 2014 autobiography for his sponsorship of a bill supported by the financial services industry that tightened rules on consumers seeking bankruptcy protections.
"The Senate was evenly split between the two parties, but one of the bill's lead sponsors was Democratic powerhouse Joe Biden, and right behind him were plenty of other Democrats offering to help," Warren wrote, the Times reported. "Never mind that the country was sunk in an ugly recession and millions of families were struggling — the banking industry pressed forward and Congress obliged."
Warren's campaign did not respond to CNBC's inquiry about her remarks. Biden's campaign and Sanders' campaign declined to comment.
In less than one full day as a 2020 presidential candidate, Biden had already received more criticism from his fellow Democrats' campaigns than any other candidate in his party.
"There's a saying in politics: 'You try to tackle the one with the ball,'" said Philadelphia-based Democratic strategist Aren Platt. "Until Biden emerged, I don't think there was a clear ball runner."
Both Warren and Sanders, who is running for president as a Democrat, have established reputations as critics and watchdogs of corporate interests and big banks.
Biden, on the other hand, was singled out for his corporate ties during his years in the Senate. With the money primary well underway, Biden's early fundraising efforts have already drawn scrutiny from Democrats who have championed small-dollar donations.
"Because Biden been in this position for so long, the people who he was friends with, his contemporaries, have risen to the highest levels," Platt said. "That's Joe Biden's social circle ... the challenge for him and his campaign will be bridging that gap."
Among the Democrats running in 2020, Warren, a former Harvard law professor, has been among the most vocal about policy. She has shared her plans for breaking up tech giants including Amazon and Apple, as well as raising revenue by slapping a new tax on corporate profits over $100 million.
Sanders proffered legislation last October to break up the big banks.
Predictably, Trump and Republicans have not held back in taking early swings at Biden.
"I'm a young, vibrant man!" Trump, 72, told reporters outside the White House on Friday. "I look at Joe, I don't know about him. I don't know." Biden is 76.
Republican officials have laid out their own strategy on Biden: compare Trump's economic record with Biden's during President Barack Obama's two-term presidency.