PHILADELPHIA — A forceful and somewhat frustrated President Obama characterized Donald Trump as a selfish, dictator-loving moron who is a threat to the very fabric of American democracy.

In his first solo campaign appearance for Hillary Clinton (and as he said, perhaps his last visit to Philadelphia as president), Obama emphasized that her victory would be a continuation of his successes.

“You don’t grade the presidency on a curve,” Obama, with sleeves rolled up, said near the famous steps of the Philadelphia Museum of Art where Rocky Balboa once ran. “This is serious business.”

Coming off the heels of a recent poll indicating a 58% approval rating—the highest since six months into his presidency in 2008—Obama riffed on the greatest hits of his administration, including a report today detailing a 5.2% rise in median income, and painted Clinton as a steady, thoughtful choice in an unsteady, insane year.

“I am really into electing Hillary Clinton,” he said, stating the somewhat obvious.

Serving as a surrogate for the campaign, during a week in which Clinton is bringing out the heavyweights of the Democratic Party while she recovers from pneumonia, Obama repeated a similar talking point that Clinton has crafted since the Democratic National Convention; Trump is not a typical Republican. So it’s OK, as a Republican, to support Clinton.

“This is a dark, pessimistic vision,” Obama said of the Trump campaign, one which he said has deviated substantially from the Party of Lincoln.

Expressing frustration both with media coverage of the election and the closeness of the race in the polls—a concern of some Democrats who have voiced consternation as to why the contest hasn’t been put away yet—Obama took off the gloves and bare-knuckle punched Trump in a vicious onslaught.

“Do you mind if I just vent for a second?” Obama said to one of the loudest cheers of the afternoon. “When we see folks talking about transparency—you want to debate transparency? You’ve got one candidate in this race who has released decades of her tax returns, the other candidate is the first in decades who refuses to release any at all.”

Trump has been dogged by constant requests to release his taxes, something that some 62 percent of Americans want to see and a normal prerequisite for the office. And as his foundation comes under more scrutiny, with potential pay-to-play scandals involved, the pressure continues to mount.

This week, both campaigns have promised to release more medical records as a reaction to Clinton’s health episode on Sunday. But Trump’s campaign manager Kellyanne Conway seemed to suggest this morning that they weren’t entirely necessary, saying that “we all have a right to privacy.” Meanwhile Trump himself is going to appear on Dr. Oz’s show, during which the scam artist physician has already promised not to ask difficult questions.

Fully embracing the role as prizefighter for Clinton, Obama also ripped Trump for his foundation’s freewheeling use of charitable contributions.

“One candidate’s family foundation has saved countless lives around the world, the other candidate’s foundation took money other people gave to his charity and then bought a six-foot-tall painting of himself,” Obama said referencing an insane anecdote from a recent Washington Post story. “He had the taste not to go for the 10-foot version,” he quipped.

Clinton’s absence from the trail did not seem to bother some supporters gathered in the Eakins Oval on Tuesday, who characterized the presidential contest as a shared interest between Obama and his one-time rival.

“We have to make sure that Trump does not get in and ruin this country,” local designer Erica Sullivan said, sporting a festive hat with pictures of Clinton and Obama embracing. “I think it sends a wonderful message to not just our country but to the entire world—that at one point in time, [Clinton and Obama] were running against each other—and now he’s embraced her in his arms and he’s supporting her. It just makes your heart feel good.”

And the importance of Pennsylvania, a state where Clinton has held a steady lead and a must-win for both candidates, was not lost on Obama. As staffers registered voters while they entered the park, the president reminded the crowd that voting registration ends on Oct. 11.

“Democracy is not a spectator sport,” Obama said in an effort to mobilize the same people that propelled him into office. Many of those young voters though aren’t as enthused with the option of Clinton as they were with Obama, a weakness which her campaign hopes to overcome with the deployment of him and others as surrogates.

So far, a simple contradiction with Trump hasn’t proven to give Clinton, the second most unpopular presidential candidate in history, the boost she needs to definitively win this race. As Obama put it once again, while the crowd voiced dissent at the mere mention of Trump’s name: “Don’t boo, vote.”