President Obama made the case for Democratic presidential nominee Hillary Clinton in Philadelphia on Tuesday, praising his former secretary of state's experience while painting Republican Donald Trump as an unqualified fraud.

Describing the November election as "a choice about the very meaning of America," Obama said the Republican Party had been preying on fear with a "dark, pessimistic" vision of the country - and contended that its nominee didn't deserve the support of working people.

Trump "spent most of his life trying to stay as far away from working people as he could," Obama told a largely welcoming crowd at Eakins Oval. "And now this guy is going to be the champion of working people? I mean, he wasn't going to let you on his golf course."

Obama also argued that questions raised about Clinton's conduct paled to those surrounding Trump. While Clinton came under fire last weekend for not revealing she had pneumonia, Obama targeted Trump's failure to disclose his tax returns.

"America's got a lot of businessmen and women who succeeded without hiding their tax returns or leaving a trail of lawsuits," Obama said.

He also contrasted the controversies around the two candidates' foundations, saying the Clinton Foundation - which has faced scrutiny over the relationships between donors and Clinton's work as secretary of state - had "saved countless lives around the world."

Trump's foundation "took money other people gave to his charity and then bought a 6-foot-tall painting of himself," Obama said, referring to a Washington Post story.

He also slammed Trump for characterizing Russian President Vladimir Putin as a strong leader. "I have to do business with Putin . . . but I don't go around saying that's my role model," Obama said. "Can you imagine Ronald Reagan idolizing somebody like that?"

As president, Obama said, he's learned that "anybody can pop off, anybody can fire off a tweet." But no one who hasn't done the job fully grasps the challenges, he said.

However, "the closest you can come to understanding what it's like is to be where Hillary's been," he said.

Declaring that Clinton had faced "what I believe is more unfair criticism than anybody out here," Obama said that "we can't afford to act as if there's some equivalence" between the two candidates.

"To be president, you have to do your homework. You have to know what you're talking about," he said. He said Clinton had learned those lessons as a senator and as secretary of state, and had demonstrated resilience.

"We take for granted sometimes what is steady and true," Obama said.

Clinton leads Trump by 2.4 percentage points in an average of recent national polls. In Pennsylvania, she is averaging a 6-point lead in polls, a margin that has diminished recently.

Pennsylvania last voted for a Republican presidential candidate in 1988. Changing demographics and electoral trends have shifted the state left, but political analysts say turnout will matter, including in Philadelphia.

Obama - who joked Tuesday that Clinton "whooped me" in the 2008 Pennsylvania primary, though "you did make it up to me in November" - told voters to not be complacent.

"You can't stay home because, oh, she's been around for a long time," Obama said, calling on supporters to "work as hard for Hillary as you did for me" and to make sure they were registered to vote by Oct. 11.

Obama, who was greeted by Sen. Bob Casey and Mayor Kenney when he stepped off Air Force One, urged supporters to also vote for Democrats down the ticket, including Katie McGinty, who is challenging Republican Sen. Pat Toomey and who also spoke at Tuesday's rally.

"If you oppose raising the minimum wage, you should vote for Trump. You should also vote for Pat Toomey," Obama said. "A Trump-Toomey economy will be right up your alley."

Toomey opposes Obamacare and the Iran nuclear deal, so "of course" Obama would support his rival, said Ted Kwong, a Toomey spokesman. But he said the senator and Obama have shared some positions - such as expanding background checks on gun purchases - and said that unlike Toomey, McGinty would be a "partisan, extremist rubber stamp."

After the rally, Obama attended a fund-raiser benefiting Clinton and other Democratic candidates at the Sonesta Hotel in Philadelphia. About 25 attendees contributed $33,400, while cochairs contributed $100,000, according to a Clinton aide.

Many at the rally said they had come to see the president speak because it was one of their last chances to do so before the president leaves office. Obama himself said it was "one of the last times I visit Philly as president."

"It's a lifetime opportunity, to see President Obama," said Luis Diaz, 30, a business administration major at the Community College of Philadelphia who has volunteered for the Clinton campaign. "I didn't want to miss it."

Some were worried, however, about stirring controversy. Mary Wade, a Clinton supporter and associate minister at Wayland Temple Baptist Church in North Philadelphia, said she was disappointed in the candidate's remarks recently saying half of Trump's supporters could go into a "basket of deplorables."

Clinton "has to be careful about not getting caught up in the negativity of the moment," Wade said. She's also concerned that "too many people are listening to the idea that [Clinton]'s not honest."

The possibility of a Trump presidency was not far from many attendees' thoughts.

"Succinctly, Trump is the main reason I'm voting for Hillary," said Larry Holmes, of Roxborough, though he said he liked that Clinton has "been through just about everything."

Not only Clinton backers were present. Yosef Weiswasser, 23, of Lakewood, N.J., said he was a Trump supporter who came to the rally to see if Obama could convince him otherwise.

While he said he liked Trump's business experience and economic proposals, he wasn't thrilled by the candidate's praise for Putin. "Obama made me a little scared to vote for Trump," he said.

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Washington correspondent Jonathan Tamari contributed to this article.