Obama asked an auditorium packed with college students who greeted him with a roaring standing ovation.
The party's "central organizing principle in foreign policy was the fight against communism and now they're cozying up to the former head of the KGB".
While the former president will be visible throughout the general election, the adviser said that Obama will not be a daily presence on the campaign trail.
When that happens, he says, people become cynical and decide not to participate in the political process - creating a vacuum that lobbyists and special interests fill.
"Which one of these people who says that they're trying to save the country and trying to save the president from himself ... ran for office and got elected?" he added. "If I was the Republicans, I would be very nervous about this".
Barack Obama delivered a very passionate speech meant to remind the citizens that they need to defend and protect Democracy and that voting is a big part of what they can actively do to achieve that. And we sure as heck are supposed to stand up clearly and unequivocally to Nazi sympathizers. "It's indifference. It's us not doing what we're supposed to do". "How hard can it be", Obama questioned, "saying that Nazis are bad?"
Democrats at the time, including Obama, denied the accusation and said those who dared to oppose the legislation were simply fear mongers or racists.
US oil prices rise as Gulf oil rigs evacuated ahead of hurricane
Oil prices were also under pressure as global shippers stopped loading Iranian oil in preparation for USA sanctions against Iran. Thanks to the US Labor Day holiday, trading volumes in both US and European crude oil futures were relatively light.
The president was widely censured by officials from across the political spectrum, and later clarified that he condemned neo-Nazis and white supremacy.
"Over the past few decades, the politics of division, of resentment and paranoia has unfortunately found a home in the Republican Party", Obama said."It did not start with Donald Trump".
Even as he has largely remained out of the spotlight, Obama made clear that he has paid close attention to the steady stream of headlines chronicling the Trump administration, saying that the news is a reminder of what is at stake in the November midterm elections.
This gloves-off performance portends a return to Obama's "fired up and ready to go" campaign style and underscores his conviction that the midterm truly is "the most important election of his lifetime". That's how real change starts, Obama said. And he implored Americans to vote for those leaders. In the social media targeted clip, he said that "basic norms and principles" have been "increasingly violated" and pushed young people to get out and vote. "You can not doubt because you don't feel sufficiently inspired by this or that candidate".
"There is a phrase that we used to use [when I was governor] for staff that acted this way, and it's called 'we know better, '" Paterson said.
Mr Trump, meanwhile, claims he fell asleep watching Mr Obama's speech.
"Because in the end, the threat to our democracy doesn't just come from Donald Trump or the current batch of Republicans in congress or the Koch brothers and their lobbyists or too much compromise from Democrats or Russian hacking", Obama said.