Urbana, Illinois (CNN) Former President Barack Obama offered his most pointed critique to date of President Donald Trump, delivering a lengthy and direct indictment Friday of the last two years in American politics by arguing the President is "capitalizing on resentment that politicians have been fanning for years."

The speech before more than a thousand students at the University of Illinois-Urbana Champaign was a preview of the message Obama will carry into the midterm elections. But it also represented the former President's most comprehensive condemnation of Republicans in Washington and the first time he has publicly criticized Trump by name in a speech.

"You happen to be coming of age" amid backlash to progress, Obama told the students. "It did not start with Donald Trump, he is a symptom, not the cause. He is just capitalizing on resentment that politicians have been fanning for years. A fear, an anger that is rooted in our past but is also borne in our enormous upheavals that have taken place in your brief lifetimes."

Obama spent a sizable portion of his remarks criticizing Republicans in Congress, saying "the politics of resentment and paranoia has unfortunately found a home in the Republican Party" over the last few decades and argued that the policies GOP leaders are pursuing aren't conservative.

The Republican National Committee responded to Obama's criticism by saying "President Obama stepped back into the spotlight to make the case that our country is on the wrong track."

"2016 is over, but President Obama is still dismissing the millions of voters across the country who rejected a continuation of his policies in favor of President Trump's plan for historic tax cuts, new jobs and economic growth," RNC spokesperson Ellie Hockenbury said in a statement. "Democrats may have a new resistor-in-chief on the campaign trail, but they'll need more than a message of resist and obstruct to win this November."

Trump responded to Obama's speech by telling a crowd in North Dakota "I watched it, but I fell asleep. I've found he's very good for sleeping."

Obama questions Republicans around Trump

While Obama only mentioned Trump by name twice in the speech, it was clear that the remarks were aimed squarely at the man he handed power to in 2017.

"It shouldn't be Democratic or Republican to say that we don't target groups of people because of what they look like or how they pray. ... We are supposed to stand up to discrimination and we are sure as heck to stand up clearly and unequivocally to Nazi sympathizers," Obama said, an apparent rebuke of Trump telling reporters after the deadly white supremacist protests in Charlottesville, Virginia that there was good "fine people on both sides."

"How hard can that be, saying that Nazis are bad?" Obama said.

And he slammed Trump for his treatment of the Department of Justice and FBI.

"It should not be Democratic or Republican, it should not be partisan to say that we don't pressure the Department of Justice or the FBI to use the criminal justice system as a cudgel to punish our political opponents," he said. "Or to explicitly call for the attorney general to protect members of own party from prosecution because elections happen to be coming up. I am not making that up. That is not hypothetical."

Trump blasted his Attorney General Jeff Sessions earlier this week, lamenting the separate indictments of two GOP lawmakers who were his earliest supporters in Congress during the 2016 election, suggesting they should not have been charged because they are Republicans.

At one point, a seemingly exasperated Obama openly questioned what happened with the Republican Party, noting that one of their early organizing principles was standing up to communism.

"What happened to the Republican Party?" he said. "Its central organizing principle in foreign policy was the fight against communism and now they are cozying up to the former head of the KGB, actively blocking legislation that would defend our elections from Russia attack. What happened?"

He added: "I don't mean to pretend I am channeling Abraham Lincoln, but that is not what he had in mind, I think, when he helped form the Republican Party. It is not conservative, it sure isn't normal. It is radical. It is a vision that says the protection of our power and those that back us is all the matters even when it hurts the country."

Obama pushes audience to vote

The remarks, Obama said, were not meant to depress the young voters in the audience, but instead inspire them to understand that their voice matters.

"Don't tell me your vote doesn't matter," he said, referring to voting as the "antidote" to all that ails Washington. "And if you thought elections don't matter, I hope these last two years have corrected the impression."

He acknowledged that politicians -- including himself -- had said similar messages about the importance of upcoming elections, but he added, "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."

The speech ended Obama's lengthy reprieve from political public life, one that has annoyed some Democrats who believed he was sitting on on a what they call a generational fight against Trump. Obama joked at the outset of the speech that he needed time away to stay married to his wife, Michelle Obama, and to spend time with his daughters. But his decision to step back into the political fray also comes at a time when Democrats, through the midterm elections, could deliver their most potent referendum on Trump to date.

Obama viewed the speech as arguably his most important of the year, his aides said, and was editing the remarks up until he touched down in Illinois.

Obama will soon take the remarks on the road, too. On Saturday, he will headline a rally for a handful of Democratic congressional candidates in California and next Thursday an event for Richard Cordray, the Democratic gubernatorial candidate in Ohio.

Obama is also planning campaign trips to Pennsylvania in September, an Obama official said, as well as a New York fundraiser for the National Democratic Redistricting Committee , an organization led by former Attorney General Eric Holder, Obama's longtime friend.

A complicated relationship

Obama has made some appearances since Trump took office -- including headlining a fundraiser for the Democratic National Committee earlier this year -- but the Trump era has complicated Obama's post-presidency. A series of former presidents have avoided critiquing their successors, and Obama has attempted to keep that tradition since he left office in January 2017.

Trump has not honored that tradition and has shown little to no regard for his predecessors, regularly bashing them on Twitter, to the media and at rallies. And the two have not talked since the inauguration in 2017, sources told CNN.

Obama's remarks represented that nonexistent relationship and while he focused some of his ire on Democrats -- arguing that the party cannot embrace the tactics of Trump as a way to get back at him -- Obama's speech seethed with his view that the Trump administration is not the new normal.

"And by the way the idea that everything will turn out OK because there are people inside the White House who secretly aren't following the President's orders," Obama said of the anonymous op-ed in The New York Times this week, published by a Senior Administration Official. "That is not a check. I am being serious here. That is not how our democracy is supposed to work."

Democrats, especially those in the room, welcomed Obama's decision to step back into the fray. The speech in the university's 1,300-person auditorium has seen sizable interest from the school's student body, according to university spokesman Jon Davis, who said they had received around 22,000 requests for tickets from students.

But Republicans also said they were eager to see Obama back in the news, arguing he is the best weapon they have to motivate their base.

"For three cycles (2010, 2012, 2014) President Obama fired up Republicans like nobody," Rep. Steve Stivers, the head of the National Republican Congressional Committee, told reporters on Friday. "And I'm happy he wants to do it again."

But Obama showed on Friday that he has a potent critique for those Republicans: Mocking them for ignoring the principles they touted during his presidency.

"Suddenly deficits do not matter, even though two years ago, when the deficit was lower, they said I couldn't afford to help working families or seniors on Medicare because the deficit was an existential crisis," he said. "What changed? What changed?"

And on jobs, he sought to remind those in the room - but more directly Republicans back in Washington - that his last two years were times of economic growth.

"I mention all of this because when you hear how great the economy is doing right now, let's just remember when this recovery started," he said, subtly knocking Trump, a president who often cites jobs numbers. "I am glad it has continued but when you hear about his economic miracle that has been going on, when the job number comes out, monthly job numbers and suddenly Republicans say it is a miracle, I have to kind of remind them, actually those job numbers were the same they were in 2015, in 2016. Anyway, I digress."

Obama out of the spotlight until now

Obama has spent much of 2018 away from the political fray, focusing on writing his book and raising money for his post-presidency foundation.

And he never said Trump's name during his fundraising speech for the DNC and instead urged Democrats to stop "moping" and get to work for candidates.

That speech, in the eyes of Obama's team, was not a preview of the former President's midterm message. Instead, Obama's advisers believe his midterm message will more closely resemble the remarks the former President delivered in South Africa as part of an event honoring the late Nelson Mandela.

That speech looked to be more inspiring, and that is exactly what Obama tried to do at the close of his remarks on Friday.

"You can be the generation that at a critical moment, stood up and reminded us just how precious this experiment in democracy really is, just how powerful it can be when we fight for it, when we believe in it," he said. "I believe in you. I believe you will help lead us in the right direction and I will be right there with you every step of the way."