Trump's rally on behalf of Republican incumbent Roger Marshall was his latest foray into conservative states where Republican candidates are on defence due to voter frustrations over the Iran war and rising prices.
"I love you Kansas, but I'm here for a guy named Roger Marshall," Trump said on Monday.
Trump pointed to widespread protests in France as a scenario that could erupt in the United States unless Republicans win. He provided no evidence.
France has seen some of the worst unrest in years as huge protests over the cost of living and underfunded public services descended into riots and looting.
Trump who has struggled to make goods and services more affordable in the US turned to anti-immigrant and anti-Muslim rhetoric, the type that he used to fuel his three presidential campaigns.
"We're not going to let that happen to this country," he said.
"When you see burning steeples and raging fires in France, just remember that is what the radical Dumocrats want to do to America."
Trump has been mocking Democrats by calling them Dumocrats.
Rights advocates have repeatedly criticised Trump for his rhetoric over the years in which he has targeted and mocked immigrants and ethnic minority groups.
Kansas, a conservative Midwestern state Trump won by 16 points in 2024, has not elected a Democrat to the US Senate in 94 years.
First-term Senator Marshall is in a close fight with Democratic candidate Adam Hamilton, pastor of a Methodist megachurch, who is running against Trump's tariff agenda and what he calls the president's "erratic leadership".
"He wants you to repent for being born White," Trump said of Hamilton.
Trump is deep into a 32-day campaign blitz, frequently going to friendly areas that he won handily in previous elections.
The latest Reuters-Ipsos poll, published on Monday, found that 31 per cent of Americans approve of Trump's performance in office, a record low for the president.
Democrats need a net gain of four seats in both the US House of Representatives and US Senate to overturn Republicans' narrow 218-214 and 53-47 majorities.
