Former President Donald Trump has surpassed President Biden's longtime fundraising lead, according to donation filings from June.

Republicans hauled in $66 million throughout the month, propelling Trump's campaign past the current president's. June saw the GOP's biggest monthly haul since 2020, according to the Washington Post.

The latest data comes after Trump's campaign boasted of out-raising Biden for most of the summer. Trump's campaign announced in early July that it and the Republican National Committee hauled in a staggering $331 million during the April through June second quarter of 2024 fundraising, topping the massive $264 million raked in by the Biden campaign and the Democratic National Committee over the same period.

And the former president's campaign spotlighted that it had $284.9 million in its coffers as of the end of June, compared to $240 million for Biden.

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Meanwhile, Biden's campaign teeters against waves of Democratic lawmakers calling on him to withdraw.

Even Biden's nominal allies in Congress have failed to give him ringing endorsements. Sen. Elizabeth Warren, D-Mass., repeatedly saying on Saturday that he's "our nominee" but he also had a "big decision to make."

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Warren also seemed to endorse Vice President Kamala Harris being the replacement if Biden did step down, singing her praises as an ideal candidate to prosecute the Democratic case against former President Trump.

"Joe Biden is our nominee, and he has a really big decision to make. Joe Biden has been a transformational president," Warren told MSNBC, going on to praise his record. "I am deeply grateful to Joe Biden for all that he has accomplished."

In the face of mounting numbers of Democrats calling on him to step down for fear he'll lose to Trump, Biden has repeatedly insisted he is staying in the race. Yet Warren, sounding like reportedly skeptical former Speaker Nancy Pelosi, D-Calif., earlier this month, appeared to give Biden yet another off-ramp.

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"Joe Biden is our nominee. As I said before, he has a really big decision to make," she said. "But what gives me a lot of hope right now is that if President Biden decides to step back, we have Vice President Kamala Harris who is ready to step up, to unite the party, to take on Donald Trump, and to win in November. Remember, 80 million people voted for Joe Biden and Kamala Harris in 2020."

Warren's interview came on the heels of Sens. Sherrod Brown, D-Ohio, Martin Heinrich, D-N.M., and Jon Tester, D-Mont., calling for Biden to leave the race this week, joining dozens of House Democrats, Fox News Digital previously reported. 

Fox News' David Rutz and Paul Steinhauser contributed to this report