Joe Biden’s team is concerned that the former vice president’s campaign strategy may not be enough to beat Donald Trump in the 2020 U.S. presidential election.

AP obtained a memo sent by Biden’s campaign manager, Jen O’Malley Dillon, warning the 77-year-old’s supporters that the Democratic nominee could still lose the political race despite approval ratings in his favor.

“The reality is that this race is far closer than some of the punditry we’re seeing on Twitter and on TV would suggest,” she wrote in the memo. 

“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.”

In the weeks leading up to the election, the outlet noted that Trump appears to be using fear tactics to win votes and has suggested that Democrats are trying to “destroy the American way of life.”

During one of his latest rallies, Trump told his supporters that Biden’s win in the election would result in “the single biggest depression in the history of our country” and “turn Michigan into a refugee camp.”

Trump has been actively hitting the campaign trail and stopped in Janesville, Wisconsin, on Saturday. Meanwhile, Biden had no public events scheduled for that day.

Biden and Trump are expected to face off in a final debate on Thursday. The Commission on Presidential Debates announced the two would discuss a variety of topics including, American Families, race in America, climate change, national security, and leadership.