Former President Donald Trump meandered Saturday through a list of grievances against Vice President Kamala Harris and other issues during an event intended to link his Democratic opponent to illegal border crossings.

A day after Harris discussed immigration at the U.S.-Mexico border, Trump spoke to a crowd in Prairie du Chien, Wisconsin, about immigration. He blamed Harris for migrants committing crimes after entering the U.S. illegally, alleging she was responsible for "erasing our border."

"I will liberate Wisconsin from the mass migrant invasion," he said. "We're going to liberate the country."

The Republican nominee also intensified his personal attacks against Harris, insulting her as "mentally impaired" and a "disaster."

"Joe Biden became mentally impaired," Trump said. "Kamala was born that way. She was born that way. And if you think about it, only a mentally disabled person could have allowed this to happen to our country. Anybody would know this."

The personal attacks have been something of a trend for Trump since Harris entered the race. In July, Trump falsely questioned Harris' racial identity during a panel with the National Association of Black Journalists.

"I didn't know she was Black until a number of years ago when she happened to turn Black and now she wants to be known as Black," Trump said at the time. "So I don't know, is she Indian, or is she Black?"

When asked in an interview with CBS News last month if he believes the personal attacks will hurt him with voters, he responded, "No, I don't think so."

Trump, meanwhile, hopes frustration over illegal immigration will translate to votes in Wisconsin and other crucial swing states. The Republican nominee has denounced people who cross the U.S.-Mexico border as "poisoning the blood of the country" and vowed to stage the largest deportation operation in American history if elected. And polls show Americans believe Trump would do a better job than Harris on handling immigration.

Trump shifted from topic to topic so quickly that it was hard to keep track of what he meant at times. He talked about the two assassination attempts against him and blamed the U.S. Secret Service for not being able to hold a large outdoor rally instead of an event in a smaller indoor space. But he also offered asides about climate change, Harris' father, how his beach body was better than President Biden's, and a fly that was buzzing near him.

"I wonder where the fly came from," he said. "Two years ago, I wouldn't have had a fly up here. You're changing rapidly. But we can't take it any longer. We can't take it any longer."

Trump repeatedly brought up Harris' Friday event in Douglas, Arizona, where she announced a push to further restrict asylum claims beyond Biden's executive order announced earlier this year. Harris denounced Trump's handling of the border while president and his opposing a bipartisan border package earlier this year, saying Trump "prefers to run on a problem instead of fixing a problem."

"I had to sit there and listen" to Harris last night Trump said, eliciting cheers. "And who puts it on? Fox News. They should not be allowed to put it on. It's all lies. Everything she says is lies."

Trump professed not to understand what Harris meant when she said he was responsible for taking children from their parents. Under his administration, border agents separated children from their parents at the U.S.-Mexico border in a policy that was condemned globally as inhumane and one that Trump himself ended under pressure from his own party.

Harris, at a rally in San Francisco, told supporters there were "two very different visions for our nation" and voters see it "every day on the campaign trail."

"Donald Trump is the same old tired show," she said. "The same tired playbook we have heard for years."

She said Trump was "a very unserious man."

"However the consequences of putting him back in the White House are extremely serious," she said.

The Harris campaign Saturday again challenged Trump to a second debate, this time in the form of a football-themed television ad. Following his Wisconsin rally, Trump traveled to Tuscaloosa, Alabama, to attend the Alabama-Georgia football game Saturday evening, and the Harris campaign premiered the ad during the game.

"Champions know its anytime, anyplace, but losers, they whine and waffle," the ad's narrator said.