President Joe Biden told Democratic donors Tuesday he wasn't confident he'd be seeking another term if his predecessor Donald Trump wasn't running for the White House, a notably candid assessment of his reelection rationale as he enters a likely rematch with his 2020 rival. "If Trump wasn't running, I'm not sure I'd be running," he said, saying Democrats "cannot let him win." The comment, made during a fundraiser at a private home outside Boston, offered perhaps the starkest rationale to date for Biden's reelection decision-making, and, according to sources familiar with the matter, took senior Biden campaign officials and advisers by surprise. "Yikes," one top campaign adviser responded upon learning of the comments. The campaign was quick to try to shrug off the president's quip as a "nothing-to-see-here" moment, pointing out that Biden has always described Trump as a unique threat to the country, and that he had expressed similar sentiments about his decision to run for president around the 2020 campaign. "President Biden said in 2020 he was running to restore the soul of our nation – he got into the race after Trump said what he did after Charlottesville – and he correctly views the former president as a unique threat to our democracy," Delaware Sen. Chris Coons, a national co-chair of Biden's 2024 campaign, told CNN. "President Biden beat Trump before and he will do it again." Biden himself appeared to walk back the comment when asked later Tuesday whether he'd still be running if Trump wasn't, telling reporters at the White House: "I expect so, but look — he is running, and I have to run." The earlier comment came as Biden began a fundraising sprint Tuesday ahead of an expensive reelection race. He's expected to raise more than $15 million over the course of five days through high-dollar fundraisers and grassroots efforts, a source with knowledge of the campaign's fundraising said. Biden headlined three fundraisers in the Boston area Tuesday, the first of seven events between now and Monday, with more scheduled for later this month. Democratic officials are looking ahead to what some believe could be a billion-dollar campaign, as Biden works to sell his reelection to a public that, at least for now, appears skeptical. Biden took on Trump directly in the first of those fundraisers, warning that his predecessor is "telling us what he's going to do. He's making no bones about it." "Trump's not even hiding the ball anymore. He's telling us what he's going to do. He's making no bones about it," Biden told donors, according to reporters in the room. Biden referenced Trump's recent focus on terminating the Affordable Care Act, as well as the former president's "vermin" remark. The former president said in a speech in New Hampshire last month: "We will root out the communists, Marxists, fascists and the radical left thugs that live like vermin within the confines of our country," and warned that "the real threat is not from the radical right. The real threat is from the radical left, and it's growing every day." The president noted that Trump did not show up to his inauguration, saying in part: "I can't say I was disappointed, but he didn't even show up." Reporters in the room said this drew some laughs from the audience. Singer-songwriter James Taylor was set to headline a later event in Boston's Theater District. Tickets for "You've Got a Friend in Joe" ran between $50 and $7,500. Two other events in the area will bring in millions more for Biden's campaign war chest. Biden also made remarks at the first fundraiser about the hostage negotiations between Israel and Hamas that broke down last week, and called for loud condemnation against what he called "the sexual violence of Hamas terrorists." "Let me be crystal clear: Hamas' refusal to release the remaining young women is what broke this deal and end the pause in the fighting. Everyone still being held hostage by Hamas need to be returned to their families immediately. We're not going to stop," he said. The president is making a final push for cash before the end of the month reporting deadline. He'll be in Los Angeles this weekend for a pair of Hollywood fundraisers, including one with a dose of star power from Stephen Spielberg, Shonda Rhimes and Rob Reiner that's hosted by decorator to the stars Michael Smith and his husband, James Costos, a former US ambassador to Spain. Last quarter, Biden and Democrats reported raising $71 million for his reelection – a solid figure that far outstripped his potential Republican rivals, but lagged behind Presidents Trump and Barack Obama at this point in their reelection. Campaign officials say the pace of fundraising has increased. November was the biggest month for grassroots donations since Biden announced reelection in the spring, an official said. So far, the campaign is putting that money to use in television ads – going on the air with a $25 million ad buy to test messaging and try to make an affirmative case for the president's reelection. Some of the ads have aired during key NFL games. Biden's reelection effort has set a record for off-year ad spending by an incumbent, according to data from AdImpact, with more than $45 million spent on pro-Biden advertising since the start of 2023. The record investment in early advertising comes from an assortment of groups supporting Biden's reelection: Biden's own campaign, which has spent about $11.3 million; an allied committee with the DNC, which has spent about $5.4 million; a joint fundraising committee, which has spent about $8.2 million; an allied super PAC, which has spent about $19.8 million; plus over a million from other, smaller groups. The total so far, over $45 million and climbing, is more than Trump and his allies spent on advertising in 2019, about $36.5 million, and far more than Obama's network spent in 2011, about $7.3 million. With its significant early investment, Biden's reelection effort has targeted key media markets in familiar battleground states – Pennsylvania, Michigan, Wisconsin, Arizona, Georgia, and Nevada. Four media markets in particular have attracted a large share of the pro-Biden ad dollars: Atlanta, the top market, where Biden's network has spent about $5.3 million; Philadelphia, where they've spent about $5.1 million; Phoenix, where they've spent about $4.2 million; and Detroit, where they've spent nearly $4 million. Las Vegas ($2.9 million), Milwaukee ($2.5 million), and Pittsburgh ($1.9 million) are the other top markets where Biden's operation has spent over $1 million. Recently, the Biden campaign has made health care a focus of its messaging, and it is airing a 60-second spot in eight different states, the above mentioned battlegrounds plus North Carolina, that features a former pediatric nurse criticizing the Trump administration's health care policies. Echoing that focus, the Biden campaign and DNC are also airing an ad in several battleground states, including Pennsylvania, Georgia and Nevada, that highlights the administration's efforts to lower prescription drug costs. The campaign also begun staffing up in key early voting states, announcing a state director this week in South Carolina, which will be an early test of Biden's support among Black voters. To this point, however, the campaign has run a relatively bare-bones operation – which officials say is intentional as they look to preserve resources for next year. — CNN