President warned that and other are "determined to destroy democracy."
Biden blasted former president at a fundraiser in New York City on Monday night.
Given current , the two men are likely in 2024 to reprise their 2020 election contest, which Biden noted.
"I don't think anyone today doubts our democracy was at stake in 2020. Thank God because of people like you we won," Biden said.
"I'm running because democracy is at stake, because in 2024, democracy is on the ballot once again," he said, adding that if he is reelected, "we will have saved American democracy."
"Let there be no question: Donald Trump and his MAGA Republicans are determined to destroy American democracy," Biden said. "And I will always defend, protect and fight for our democracy."
Biden also drew a contrast between how he views Russian President Vladimir Putin and how Trump does.
"I will not side with dictators like Putin. Maybe Trump and his MAGA friends can bow down, but I won't," Biden said.
Steven Cheung, a Trump campaign spokesman, in a statement in response to Biden's fundraiser comments suggested Biden was the real threat to democratic values.
"Crooked Joe Biden is the one who has weaponized his Justice Department to go after his main political opponent — President Trump," Cheung said.
"He has directed these illegal witch-hunts to interfere in an election where President Trump is leading him in the polls."
Trump has been indicted four times on criminal charges since the spring, with two of those cases lodged by special counsel Jack Smith, who was appointed to that role by Attorney General Merrick Garland.
Smith's office is prosecuting Trump in federal court in Washington, D.C., for alleged crimes related to his effort to undo his loss in the 2020 election, and in Florida federal court for retaining classified records after leaving the White House and allegedly trying to hide them from government officials.
Trump is charged in state court in Atlanta with alleged crimes related to his attempt to reverse Biden's victory in the 2020 presidential election in Georgia. He also is charged in New York state court with allegedly falsifying business records in connection with a 2016 hush money payment to porn star Stormy Daniels.
