Larry Snelling, Chicago’s police superintendent, said the city was on high alert with a huge police presence deployed on the streets.
At a press conference on Monday, he said his officers have undergone extensive training on de-escalation to ensure the demonstrations remained peaceful.
“What we will not tolerate is intimidation. We will not tolerate violence,” he warned.
Some local businesses had boarded up their windows in anticipation, while local courts said they were prepared to process mass arrests.
Brandon Johnson, the mayor, said the city had been preparing for potential unrest for months. “We are ready,” he said.
Donald Trump highlighted the protests on his social media platform, writing: “The radical Left protesters in Chicago are going after the Democrat Party because they know they are weak and ready to break into a full-blown party of socialism.”
The Democrats’ stance on Gaza threatens to be the one issue that could divide the party, which hopes to project an image of unity as it gathers to support Ms Harris, the first woman of colour to top a major party’s presidential ticket.
Ms Harris and Minnesota governor Tim Walz, her running mate, have made “joy” the unofficial theme of their campaign, but progressive voters said their votes could not be taken for granted against the backdrop of Israel’s war in the Gaza Strip.