Speaking at a Thursday afternoon rally on behalf of Hillary Clinton in Miami Gardens, Florida, Obama didn't hold back, shredding Rubio for supporting Trump despite previously calling him a "con artist" and an "erratic individual."
"I agree with the U.S. senator, a Republican, who a while back said that we can't afford to give the nuclear codes of the United States to an erratic individual," Obama said to cheers from the crowd. "By the way, you know who said that? Marco Rubio!"
Obama cited Rubio's comments from February, when he called Trump a "con artist."
"Say it again!" an attendee shouted.
"Do you want me to say it again?" Obama asked. "He said, Marco Rubio said, this was a dangerous con artist who spent a lifetime, spent a career, sticking it to working people! Now that begs the question, since we're in Florida: why does Marco Rubio still plan to vote for Donald Trump?"
Obama acknowledged the differences between the two major parties, but suggested that politicians shouldn't make decisions solely on the basis of partisanship or the advancement of their own careers.
"Trump didn't come out of nowhere," he said, citing the rise of Republican politicians and far-right news outlets who have promoted conspiracy theories like birtherism, the long-refuted claim that Obama was not born in the United States.
"They've been saying crazy stuff, and there are a lot of politicians like Marco Rubio who know better, but they just look the other way," he said.
Obama blamed politicians like Rubio for encouraging far-right conspiracy theories and obstructing Democrat-backed political initiatives to gain popular support.
"They just stood by and said nothing, even though they knew better, while their base actually started believing some of this stuff," he said.
He went on to shred Republican members of Congress for standing by Trump through a flood of controversies, including his "bromance with Putin," his comments calling Mexican immigrants "criminals and rapists," and his attacks on a Gold Star family.
"I don't give a lot of credit to folks who are just now trying to walk away from Trump. Although I will say I'm even more confused by Republican politicians who still support Donald Trump," Obama added, turning his attention back to Rubio. "How can you call him a con artist and dangerous and object to all the controversial things he says and then say, but I'm still going to vote for him? Come on, man."
But he wasn't done.
Obama gave Rubio credit for condemning Trump's claims that the election will be rigged, but pointed out that Rubio has not withdrawn his support.
"He's refuting the dangerous and unprecedented claims of a candidate he says he's still going to vote for!" Obama said. "Which just gives you one more bit of proof that Marco seems to just care about hanging onto his job."
While Obama wrapped up his speech on a more optimistic note, citing healthcare, immigration reform and the economic recovery as successes, he apparently couldn't resist the opportunity to take one last jab at Rubio before he left the stage.
"Progress is on the ballot. Stability is on the ballot. Tolerance is on the ballot. Justice is on the ballot. Equality is on the ballot. Our democracy is on the ballot. Hillary Clinton will advance those things," Obama said. "Donald Trump wants to reverse progress. Marco Rubio wants to help him."