US President Barack Obama warned America that “democracy itself” is on the ballot in November’s presidential election, as White House concern grows about the lasting impact of Republican Donald Trump’s scorched-earth campaign.

“Civility is on the ballot. Tolerance is on the ballot. Courtesy is on the ballot. Honesty is on the ballot. Equality is on the ballot. Kindness is on the ballot,” Mr Obama said at a fiery campaign event for Hillary Clinton in Cleveland.

“All the progress we made in the last eight years is on the ballot,” he said. “Democracy itself is on the ballot right now.”

Camera Icon Democratic presidential nominee Hillary Clinton. Credit: AP Camera Icon Republican presidential candidate Donald Trump. Credit: AFP, Getty

He called out Trump for claiming the election is rigged against him.

Mr Obama told Hillary Clinton supporters that some nations do rig elections. He said they are tyrannies that oppress their people. Mr Obama said the US has fought against those things.

Mr Obama said in a democracy, a politician can’t just ban journalists “that you don’t like.”

He cited the US Constitution’s First Amendment protections for freedom of the press.

Camera Icon US President Barack Obama arrives to speak at a Hillary for America campaign event in Cleveland, Ohio. Credit: AFP

A few minutes into Mr Obama’s campaign riff selling his record over the last eight years in the White House, the outgoing 44th president noticed a commotion in the crowd — populated largely by young voters and many families with young children.

“Our businesses have turned job losses into 15 million new jobs, we slashed our dependence on foreign oil,” Mr Obama said trailing off, “hold on a second, young man. Don’t be interrupting everybody, come on. Come on, sir. Come on.” Mr Obama tried to lead a chant to drown the man out. “Everybody — come on, everybody. Let’s do our little chant. Hillary! Hillary!”

Camera Icon A demonstrator holds up a picture of former US President Bill Clinton that reads "RAPE" as US President Barack Obama speaks at a Hillary for America campaign event in Cleveland, Ohio. Credit: AFP

“I notice this has been happening everywhere,” Mr Obama said. “If you’re confident about the other guy, just go to his rallies. I feel confident about my candidate.”

“That’s a better way for you to spend your time. Unless you’re just being paid to be here. In which case hey, you know, everybody got to make a living. Where was I?”

Camera Icon Democratic presidential nominee Hillary Clinton (R) shakes hands with husband and former U.S. President Bill Clinton (L). Credit: AFP, Getty Camera Icon Juanita Broaddrick sits before the town hall debate. She has long accused Bill Clinton of raping her. Credit: AFP, Getty

The hard-fought White House race has turned even more nasty in recent weeks, as Mrs Clinton has pulled away from Trump in the polls.

Since Trump declared himself free of the shackles of Republican orthodoxy, Mrs Clinton’s speeches have been repeatedly interrupted by people shouting that her husband “Bill Clinton is a rapist!”