Former Vice President Joe Biden sought to link President Trump to what he described as “forces of darkness” and hatred, in a blistering speech to a Martin Luther King Jr. Day breakfast sure to keep speculation alive about a possible 2020 bid.

The former VP spoke on a day when numerous potential or declared presidential candidates were participating in MLK Day events, including Sens. Kirsten Gillibrand, D-N.Y.; Bernie Sanders, I-Vt., and Cory Booker, D-N.J.

Just hours earlier, California Democratic Sen. Kamala Harris formally announced her presidential run in an interview. And preceding Biden at the National Action Network breakfast was former New York City Mayor Michael Bloomberg, who hinted at 2020 considerations when he quipped that he wanted to get “pointers” from Biden on what it’s like to live in Washington.

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But Biden, who once engaged in a war of words with Trump over who would win in a fight, continued to show no reservations about tearing into president – signaling he would run a sleeves-rolled-up, aggressive campaign should he decide to launch one.

Recalling the “hate that cut” down King in 1968, Biden said “forces of darkness” continue to nurture that undercurrent.

“They have been deliberately reawakened again … it’s not an accident,” Biden said, citing the 2017 white supremacist rally in Charlottesville, Va., where a counter-protester was killed and dozens were injured in a car attack.

Trump was widely criticized for his initial remarks on the rally and the violence, saying there were some “very fine people on both sides.”

Biden said: “Having a president of the United States make a moral equivalence between those who are spreading the hate and those who are opposing it … no president since the Civil War has ever, ever, ever uttered words like that.”

Without addressing his 2020 intentions, Biden spoke in broad terms as he called for people to “speak out” and said, “This is not our America.”

The address included a few stump speech-like lines, referencing his well-known affinity for Amtrak and urging an increase in the minimum wage nationally.

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“What the hell are we arguing about a $15 minimum wage for, why is that even a question?” he asked.

Biden, however, would face an already-crowded Democratic field if he enters – as well as lingering questions about whether the old guard of the Democratic Party should step aside to allow a younger, more diverse class of competitors duke it out for the party mantle in 2020. His two-time running mate, former President Barack Obama, recently called for "new blood" in politics.

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Trump, meanwhile, celebrated the holiday and honored King’s legacy on Monday, disregarding Biden’s criticism.

“Today we celebrate Dr. Martin Luther King, Jr. for standing up for the self-evident truth Americans hold so dear, that no matter what the color of our skin or the place of our birth, we are all created equal by God. #MLKDay,” he tweeted, along with a presidential proclamation.

An error occurred while retrieving the Tweet. It might have been deleted.

Trump and Vice President Pence also visited and laid a wreath at the Martin Luther King Jr. Memorial in Washington.