The Biden campaign is latching on to Trump’s taunt over Biden listening to scientists, with the former vice president tweeting ”…yes,” in response to one report reading "Trump: Biden will 'listen to the scientists' if elected."

Trump, at a rally in Carson City, Nevada, Sunday night, mocked Biden for saying if elected he would “listen to the scientists” regarding the ongoing pandemic which has left nearly 220,000 Americans dead.

“If I listen totally to the scientists, we would right now have a country that would be in a massive depression,” said Trump, who also continued to criticize Biden’s use of circles at campaign events for social distancing. Trump also claimed Biden would create lockdown measures that would lead to the "Christmas season" being canceled.

Biden spokesperson Andrew Bates, responding to the attack in a statement Monday, turned to the economy.

"Now new coronavirus cases are surging and layoffs are rising. If Donald Trump had listened to Joe Biden when he urged him not to trust the Chinese government over his own scientific advisers about this crisis, he wouldn't be the worst jobs president since 1929,” Bates said. 

Biden’s rapid response spokesperson Rosemary Boeglin also took aim at the attack tweeting, “Closing message, 8 months into a pandemic he’s let spin out of control: “President Donald Trump sought to insult former Vice President Joe Biden on Sunday by saying that his Democratic opponent would listen to scientists if elected president."

Shortly afterward, the Biden campaign announced Biden’s 11th negative COVID-19 test since Trump tested positive earlier this month.

"Vice President Biden underwent PCR testing for COVID-19 today and COVID-19 was not detected,” the campaign said in a statement to reporters.

-ABC News' Will Steakin and Molly Nagle

While Trump is slated to hold a two rallies in Arizona Monday, Biden is off the trail and prepping for their final one-on-one match up in Nashville on Thursday.

A source familiar with Biden’s schedule tells ABC News that the former vice president is meeting with advisers and doing debate prep.

He broke from that debate prep and stopped by The Queen theater in Wilmington, Delaware, to tape an interview for an episode of the CBS News program "60 Minutes" that is slated to air Sunday.

Over the weekend, the Commission on Presidential Debates announced the topics the moderator, NBC News' Kristen Welker, has selected. Her list, subject to change: Fighting COVID-19; American Families; Race in America; Climate Change; National Security; Leadership.

The debate will start at 9 p.m. ET and run for 90 minutes without commercial interruption, the commission said.

-ABC News' Molly Nagle

In the crucial final two weeks of the election, the Trump campaign is being outspent by the Biden campaign on television ads $45 million to $54 million -- a spending gap that is further widened as pro-Biden outside groups are spending more than three times the amount pro-Trump outside groups are on the ad war.

In Iowa, for instance, Trump had been completely off the air since July and is only now set to go back up in a state where polls currently show a more competitive race than 2016, when the president won by over nine points. Sources pointed to the president's recent Iowa rally as a way the team hoped to make up for the lack of ad spending in the state.

The president's team has also been pulling back spending in other states crucial to his White House win four years ago. Earlier this month, the campaign canceled more than $2 million worth of airtime in Ohio, pushing back its return to the state until the last two weeks of October after being mostly quiet since the summer. It's now among Trump's top markets entering the home stretch, with $5.3 million reserved for airtime from Oct. 20 through Election Day.

And in key states like Pennsylvania, Michigan and Wisconsin, the Trump campaign is being vastly outpaced by the Biden campaign. From September through Election Day, Trump has invested about $31 million in those three states, compared to Biden who has poured more than $110 million in those states during the same period.

When asked about cutting ads in crucial swing states, Trump campaign Deputy National Press Secretary Samantha Zager called TV ads "a small piece of the voter outreach puzzle" and said that "it makes no sense to run TV ads in states we know we’re going to win, and in other states, they’re a useful tool to reach the right voters with the right message."

Needless or not, from Oct. 20 through Nov. 3, the Biden campaign, the Democratic National Committee and pro-Biden outside groups have reserved a total of $141.5 million of airtime, twice the $70.8 million that the Trump campaign and pro-Trump outside groups have reserved during the same period, according to ad spending data from media research firm CMAG.

-ABC News’ Will Steakin and Soo Rin Kim

Trump, down in the polls to Biden and facing a once-unimaginable cash crunch, has been forced to spend the dwindling final weeks of his reelection fight on defense.

Out of the 13 rallies in nine states that the president has scheduled since returning to the campaign trail after being diagnosed with COVID-19, only one, Nevada, would be a pickup for the president -- the others show a president needing to spend valuable time and money predominantly campaigning in states he won in 2016, including some he won handily like Iowa.

Publicly, the Trump campaign remains optimistic. 

Internally, the Trump campaign is increasingly worried that the president's chances of winning North Carolina, a state the team has heavily invested in and views as essential for Trump's path to victory, has all but evaporated. The campaign had viewed the state as "super safe" as recently as just a few weeks ago, sources told ABC News. 

Advisers now fear that, because the state counts and reports both day-of and mail-in votes together on election night, losing North Carolina could be a clear white flag.

And with the fallout from the first debate and Trump's contracting the novel coronavirus, some aides inside the campaign have started to grow fearful of what their employment prospects may look like if the president were to lose, sources said.

-ABC News’ Will Steakin and Soo Rin Kim