US President Barack Obama warned that "democracy itself" was on the ballot in this year's presidential election during a fiery campaign event in Cleveland, Ohio on Friday.

In what was perhaps his most stirring speech yet against Donald Trump, Obama denounced the Republican candidate as a "dictator-in-the-making." The president also singled out Trump's purported business acumen and newfound rage against the "global elite" for ridicule.

"This is a guy who spent all his time hanging around, trying to convince everybody he was a global elite ... and flying around everywhere and all he had time for was celebrities," Obama told a group of young voters. "Suddenly he's going to be the champion of working people? Come on, man."

Long-term problems for democracy

On a more somber note, Obama highlighted that the toxic nature of this year's presidential campaign could pose long-term problems for US democracy.

"Civility is on the ballot," Obama said. "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," he continued. "All the progress we made in the last eight years is on the ballot - democracy itself is on the ballot right now."

Obama pointed to Trump's claims that the election was "rigged" against him. Trump has encouraged voters to monitor electoral fraud in Pennsylvania and elsewhere. The president likened such tactics to that of "tyrannies."

In the last week, Trump has declared himself exempt from traditional political etiquette and launched a series of inflammatory accusations directed at Democratic nominee Hilary Clinton, as well as her husband.

Trump has also claimed that the "global elite" was working against him. "Hillary Clinton meets in secret with international banks to plot the destruction of US sovereignty in order to enrich these global financial powers, her special interest friends and her donors," Trump told supporters in Florida on Thursday.

Ohio: crucial swing state

Ohio, with its diverse mix of urban and rural areas, has traditionally been a key swing state in presidential elections. Many political commentators even regard it as a barometers for swings in the US' political climate.

This year, it is one of the states that polls suggest could go either way. The other so-called "purple states" are Nevada, North Carolina and Florida.

dm/jm (AP, AFP)