"Just a glance at recent headlines should tell you this moment really is different", Mr Obama said.
The speech is Mr Obama's first big step into the campaign for the midterm elections.
Obama plans to hit the campaign trail for Democratic candidates in competitive races all across the country through October, appearing first in California on Saturday and OH next week.
Next week, Obama plans to campaign in OH for Richard Cordray, the Democratic nominee for governor, and other Democrats.
But California Republicans said Mr Obama's appearance would have little impact, and may even help their party.
Launching an unprecedented attack on Trump and his policies, Obama said: "It did not start with Donald Trump".
Obama has spent much of his post-presidency on the political sidelines, but an adviser says that in the speech he will be more "pointed" in his reflection on the current political environment, including President Donald Trump.
His appearance - one day after a strongly worded critique of Mr Trump at University of IL at Urbana-Champaign - touched on themes of retirement security, climate change and education.
The former president's remarks in IL came ahead of a series of campaign stops to help fellow Democrats running in the November midterm elections.
During a speech at the University of IL at Urbana-Champaign on Friday, Obama said the country is in a "backlash" moment.
Obama's more veiled attack was a reference to the President's tweet about Attorney General Jeff Sessions last Monday that also lamented the indictments of GOP Reps. "Barack Obama wasn't ready for America", said Bongino. The Trump administration was under fire from Democrats for its response and handling of recovery efforts on the island.
The former president also criticized the claims of an anonymous New York Times op-ed, which said many staffers are "working diligently from within" to keep Trump from enacting damaging policies. The speech will be a preview of the argument Obama will make this fall campaign season.
Following a fiery appearance in his home state of IL, former President Barack Obama brought a softer tone Saturday to Orange County, California - a traditional GOP stronghold.
"He is a re-energizer for progressives who care about what's at stake and a reminder for independents that we can have a President who isn't an embarrassment to the country", said Jesse Ferguson, a Democratic strategist who worked on Hillary Clinton's 2016 campaign.
"Demagogues promise simple fixes for big problems", Obama said, swiping at Trump.
"I'm sorry, I watched it, but I fell asleep", he said at a campaign appearance in Fargo, North Dakota.
Obama thundered, in reference to the revelations by investigative journalist Bob Woodward whose new book describes Trump's aides battling to rein in an angry, uninformed president that "That's not how our democracy is supposed to work".