In his most pointed critique yet, Obama said Hillary Clinton's campaign acted too cautiously out of a mistaken belief that victory was all but certain.
"If you think you're winning, then you have a tendency, just like in sports, maybe to play it safer," Obama said in the interview with former adviser and longtime friend David Axelrod, a CNN analyst, for his "The Axe Files" podcast.
The president said Clinton "understandably ... looked and said, well, given my opponent and the things he's saying and what he's doing, we should focus on that."
Trump took exception to this critique, tweeting out later in the day that "President Obama said that he thinks he would have won against me. He should say that but I say NO WAY! - jobs leaving, ISIS, OCare, etc."
Obama stressed his admiration for Clinton and said she had been the victim of unfair attacks. But, as he has in other exit interviews, Obama insisted that her defeat was not a rejection of the eight years of his presidency. To the contrary, he argued that he had put together a winning coalition that stretched across the country but that the Democratic Party and the Clinton campaign had failed to follow through on it.
"I am confident in this vision because I'm confident that if I -- if I had run again and articulated it -- I think I could've mobilized a majority of the American people to rally behind it," the president said.
"See, I think the issue was less that Democrats have somehow abandoned the white working class, I think that's nonsense," Obama said. "Look, the Affordable Care Act benefits a huge number of Trump voters. There are a lot of folks in places like West Virginia or Kentucky who didn't vote for Hillary, didn't vote for me, but are being helped by this. ... The problem is, is that we're not there on the ground communicating not only the dry policy aspects of this, but that we care about these communities, that we're bleeding for these communities."
Clinton spokesman Brian Fallon said via email that the campaign declined to comment.
Axelrod, in an interview with The Washington Post, said he believed Obama went further than he had before in critiquing Clinton's campaign.
"This was all in service of making the point that he believes that his progressive vision and the vision he ran on is still a majority view in this country," Axelrod said. "He chooses to be hopeful about the future."
Obama could not have run again; the 22nd Amendment of the Constitution states that "No person shall be elected to the office of the President more than twice."
Still, Obama's suggestion that he could have won if he ran stoked debate Monday among political observers.
Former House speaker Newt Gingrich, a Republican who has been an adviser to Trump, said in an interview that "Obama doesn't know and neither does anyone else. Obama would have increased the turnout in the African American community, but he also might have increased the repudiation of him among those who felt they were betrayed.
"All of the lies he told about Obamacare, 'keeping your doctor' ... would have come back to haunt him. It would have been a totally different race."
Steve Hildebrand, a Democrat who oversaw Obama's 2008 campaign in battleground states, said the president had an ability to communicate with lower-income workers that Clinton lacked. He said he sent the Clinton campaign 15 emails in which he said he told them "you are not communicating with lower-income workers, you are not connecting with them."
In the podcast interview, Axelrod did not press Obama on many of the most controversial parts of his presidency, such as not taking action to prevent the deaths of hundreds of thousands of people in Syria.
The president, who has done relatively few interviews with mainstream media organizations, repeated his long-stated complaint that the media has filtered his message and that he is subject to unfair criticism by outlets such as Fox News.
Obama also blamed some of his problems during his presidency on Senate Majority Leader Mitch McConnell, R-Ky., a longtime adversary who famously said in 2010: "The single most important thing we want to achieve is for President Obama to be a one-term president."
McConnell failed in that goal, but Obama said the senator was successful in blocking many of his initiatives and setting the groundwork for Trump's victory.
McConnell's strategy from a "tactical perspective was pretty smart and well executed," the president said. The Republican leader found ways to "just throw sand in the gears" in a manner that fed into people's beliefs that things were going badly. Obama said that, as a result, Republicans blocked action that could have helped more people recover from the Great Recession.
The strategy, Obama maintained, was that "if we just say no, then that will puncture the balloon, that all this talk about hope and change and no red state and blue state is -- is proven to be a mirage, a fantasy. And if we can -- if we can puncture that vision, then we have a chance to win back seats in the House."
A McConnell spokesman did not respond to a request for comment.
Obama stressed that he doesn't plan to get involved in day-to-day responses to a Trump presidency, just as former president George W. Bush has remained mostly on the sidelines during the Obama years. But Obama made it clear that he will be more of an activist in the long run. He said he plans to help mobilize and train a younger generation of Democratic leaders and will speak out if his core beliefs are challenged. He also said he is working on writing a book.
His post-presidential "long-term interest," Obama said, is "to build that next generation of leadership; organizers, journalists, politicians. I see them in America, I see them around the world -- 20-year-olds, 30-year-olds who are just full of talent, full of idealism. And the question is how do we link them up? How do we give them the tools for them to bring about progressive change? And I want to use my presidential center as a mechanism for developing that next generation of talent." He said he didn't want to be someone "who's just hanging around reliving old glories."
Obama in the interview also reflected on his years at college, particularly Columbia University, from which he graduated in 1983. He said he was rereading "old journals" and letters to girls that he was "courting," and found them unreadable. He found himself to be "wildly pretentious," recalling how he begged off going to parties so he could read the French philosopher Jean-Paul Sartre. The women on campus found him "too intense," he said.
Looking back, said the president of the United States, "I should've tried, like, you know, 'Wanna go to a movie?' "