The Biden campaign sent out a three-page memo to supporters Saturday warning that President Trump can still win and the race is "neck and neck" in certain critical battleground states, including Arizona and North Carolina. 

Jen O'Malley Dillon, Joe Biden's campaign manager, cautioned supporters against complacency, pointing to uncertain polls and lessons learned from Trump's upset win in 2016.

"[T]he reality is that this race is far closer than some of the punditry we’re seeing on Twitter and on TV would suggest," Dillon wrote in the memo obtained by Fox News. 

Dillon cautioned that polling showing Biden ahead may not be accurate.

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“[E]ven the best polling can be wrong and that variables like turnout mean that in a number of critical swing states we are fundamentally tied," Dillon wrote. 

The message to supporters was to press on the gas in the final stretch to drive up turnout and donations. "We need to campaign like we are trailing," the memo said. 

Democratic presidential candidate former Vice President Joe Biden speaks at the Carpenters Local Union 1912 in Phoenix, Thursday, Oct. 8, 2020, to kick off a small business bus tour. (AP Photo/Carolyn Kaster)

Democratic presidential candidate former Vice President Joe Biden speaks at the Carpenters Local Union 1912 in Phoenix, Thursday, Oct. 8, 2020, to kick off a small business bus tour. (AP Photo/Carolyn Kaster)

“If we learned anything from 2016, it’s that we cannot underestimate Donald Trump or his ability to claw his way back into contention in the final days of a campaign, through whatever smears or underhanded tactics he has at his disposal," Dillon wrote. 

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Dillon's state-of-the-race memo outlined what's positive in the Biden campaign in the final days of the election, including Biden's financial advantage, nearly 3,500 staff working to organize in battleground states, and the "largest and best-resourced vote protection program in history."

She said while Biden's campaign has spent more than any presidential campaign in history on advertising, the advantages could be instantly wiped away if more billionaires write checks to pro-Trump super PACs.

This was likely a reference to casino magnate and Republican megadonor Sheldon Adelson and his wife Miriam contributing $75 million last month to a super PAC backing Trump.

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President Donald Trump arrives to speak during an event on "Protecting America's Seniors," Friday, Oct. 16, 2020, in Fort Myers, Fla. (AP Photo/Evan Vucci)

President Donald Trump arrives to speak during an event on "Protecting America's Seniors," Friday, Oct. 16, 2020, in Fort Myers, Fla. (AP Photo/Evan Vucci)

Over the next three weekends, the campaign needs to "double our capacity" on voter outreach in 17 battleground states and raise $234 million by Nov. 3, the memo said. If they exceed that amount, Biden can boost efforts in Texas, a traditionally red-leaning state that Democrats have been trying to flip for years. 

The campaign also is gearing up for potential problems at polling places and contested votes, with 17 state-specific voter hotlines and "thousands of lawyers and volunteers" working on voter protection.

“We cannot become complacent because the very searing truth is that Donald Trump can still win this race," Dillion wrote, "and every indication we have shows that this thing is going to come down to the wire."