Joe Biden’s middling $15.2 million third-quarter fundraising haul is raising fresh questions about whether the former vice president’s campaign can withstand a new onslaught of Republican ad attacks while simultaneously waging a battle for the Democratic nomination.

Biden’s campaign has long framed his candidacy around the idea that he can beat Trump in a head-to-head contest, particularly in the battleground states that were central to Trump’s 2016 victory over Hillary Clinton.

But Biden’s polling numbers in the Democratic primary have declined in recent months, and his fundraising has also lagged — he collected $7 million less between July and the end of September than in the second quarter.

His latest fundraising round was more than $9 million behind his closest rival in the polls — Elizabeth Warren. His total also ran well behind Pete Buttigieg and Bernie Sanders.

That’s a problem for a candidate who is seeking to compete in all four early states and also build out his campaign infrastructure in the 14 states that will vote on Super Tuesday.

Making matters worse, Donald Trump and Republicans have announced they’ll launch $10 million in negative TV ads — with $1 million targeted at the early nominating states alone — pushing the president’s claim that Biden and his son Hunter engaged in corruption in Ukraine.

Trump — who is facing an impeachment inquiry that centers on his asking the president of Ukraine to investigate Biden and his son’s business dealings — and Republicans together raised an eye-popping $125 million in the third quarter .

“The reason it’s happening is because Trump sees Biden as his biggest threat,” said Patti Solis Doyle, a former Barack Obama adviser and onetime Biden chief of staff. “In some ways, it’s a good thing because it frames it as a Biden versus Trump race. However, if Biden cannot compete on the other metrics in the field, then even that [advantage] goes away for him.”

The surge in anti-Biden messaging comes at a pivotal time in the Democratic campaign, as Warren surges in the polls and makes gains across different demographic groups. Between the campaign’s need to spend to preserve its position in the primary and its need to defend against the flurry of GOP attacks, Biden will be fighting on two fronts, amid new doubts over whether Biden will have the resources necessary to do both.

And Biden must continue to demonstrate vitality to donors or he’ll face a fate similar to what Jeb Bush experienced in a crowded 2016 primary race in which the former Florida governor steadily fell behind, unable to recover from a surging Trump.

David Kochel, a chief strategist in Bush’s 2016 presidential campaign, said like Biden, Bush was an early front-runner with high name ID who raised “a boatload” the first quarter but failed to grow after big donors maxed out. He said Biden is in danger of following a similar trendline because of the nature of his fundraising base.

“The former vice president, with all the high-dollar contacts around the country — you do all the big fundraisers in the big cities. Once you do that, that’s it. If you don’t have that perpetual, low-dollar fundraising machine, you can’t compete,” Kochel said, noting the massive figures reported by Biden’s top rivals. “Biden looks like he can’t compete with Warren, Bernie and Buttigieg. How’s he going to compete with Trump?”

A Biden campaign statement Thursday on its fundraising disputed the notion that he wasn’t building momentum or that his donors had maxed out. The last week of the quarter was Biden’s best week since early May, according to the campaign, and 98 percent of its donations were $200 or less.

The Biden campaign is attempting to fend off incoming Trump ads by aggressively lobbying cable networks against airing a new Ukraine-oriented spot that it says “spreads false, definitively debunked conspiracy theories.” The campaign on Friday served Facebook with the same letter and is expected to do the same with local TV stations.

This week, it announced its own early state digital and TV ad buy — $6 million worth.

Biden himself fought back against Trump in a Nevada appearance earlier this week.

“You’re not going to destroy me,” Biden declared. “And you’re not going to destroy my family. I don’t care how much money you spend or how dirty the attacks get.”

Since the first reports that Trump asked Ukraine’s president to investigate Biden, the former vice president’s campaign has attempted to raise money off the scandal, crafting fundraising pitches around the latest headlines. On Friday, a new online fundraising request urged potential donors to chip in to a new “Beat Trump Rapid Response Fund.”

“Trump declared war on our campaign today with a $1,000,000 TV ad campaign in the first four primary states,” a request to donors blared, then asked for a $5 donation.

The Biden campaign says the attacks only validate its long-standing argument that Biden is the biggest threat to Trump’s reelection. And it has repeatedly pointed to Trump’s actions — including asking both Ukraine and China to investigate the former vice president — as a sign that Biden is the Democrat the president fears most as his general election opponent.

"This is happening for one reason: Donald Trump is trying to choose his opponent, and views Joe Biden as his biggest threat. Why else would he be targeting these ads in early primary states? He knows Biden has the durability to withstand them, so he's trying to take him out early,” a Biden adviser said Friday. “And what's undeniable is he's going to do exactly this or worse to whoever the Democratic nominee is — and no one else has proven they can handle it and fight back like Biden has."