Former President Barack Obama said he was re-entering the political stage on Friday to tell Americans to vote in what he called the most important election of his lifetime.

In a speech at the University of Illinois, Obama called out President Donald Trump by name, along with the Republican Party, for embracing demagoguery and division, leading to the erosion of American norms that helped make the country great. The cure for America's "current funk" is voting, he said, telling young people that they have the power to change the world if they mobilize.

"Just a glance at recent headlines should tell you that this moment really is different, the stakes really are higher. The consequences of any of us sitting on the sidelines are more dire," Obama said, speaking, "as a fellow citizen, not as an ex-president."

Advisers had cast the speech, which came as Obama accepted an ethics in government award, as the moment he would re-engage in politics after spending most of his post-presidency on the partisan sidelines. Obama did so with his most direct comments about Trump since the start of his presidency — he rarely mentions Trump by name.

Obama called the times we are living in extraordinary and dangerous times in which politicians on the right have taken advantage of people's simmering economic insecurity.

"Over the past few decades the politics of division and resentment and paranoia has unfortunately found a home in the Republican Party," he said, highlighting its attempts to roll back the social safety net, cut taxes without raising more revenues, rejecting climate change and more.

But Trump is a "symbol, not the cause" of the party's appeals to tribalism and to fear, which wouldn't work in a "healthy democracy," Obama said.

Yet Obama also called out his actions directly, including threatening the freedom of the press and pressuring the Department of Justice to investigate political opponents and protect members of political allies ahead of elections, as Trump has recently done — including during the speech.

"We're supposed to stand up to bullies, not follow them," Obama said. "We're supposed to stand up to discrimination, and we're sure as heck supposed to stand up clearly and unequivocally to Nazi sympathizers. How hard can that be, saying that Nazis are bad?"

The cure for such actions, Obama said, is by making sure to vote in November's midterm elections.

"This is not normal ... but here's the good news: in two months, we have the chance — not the certainty but the chance — to restore some semblance of sanity to our politics," he said.

Trump responded to Obama's comments at a speech in North Dakota: "I watched it, but I fell asleep. I found he's very good. Very good for sleeping."

The Republican National Committee cast Obama as the "resistor-in-chief" and said he was dismissing the people who voted Trump into office.

Republican Sen. Lindsey Graham of South Carolina tweeted that the speech made it more likely that Trump would get re-elected.

"In fact, the best explanation of President Trump's victory are the 'results' of the Obama Presidency!" he said.

The speech came as Trump told reporters that the Justice Department should investigate the identity of the senior White House official whose anonymous New York Times op-ed this week said people inside the White House are trying to stop Trump from achieving his worse impulses.

Obama touched on that article as well, saying people inside the White House not following the president's orders shouldn't be seen as a check on Trump's power: "They're not doing us a service by actively promoting 90 percent of the crazy stuff that's coming out of this White House and then saying, 'Don't worry, we're preventing the other 10 percent.'"

More than 17 times as many University of Illinois students registered to hear the speech as there are seats in the auditorium. The News-Gazette reports 22,611 students registered before a ticket lottery portal closed last Friday for the some 1,300 available seats in Foellinger Auditorium.

University special events director Laura Wilhelm-Barr says Foellinger was being closed part of Thursday and all day Friday ahead of the speech.

Larger campus venues are hosting other events, with concerts scheduled Wednesday and Friday nights at State Farm Center and the Krannert Center for the Performing Arts booked for its 50th anniversary celebration on Friday night.