Kamala Harris and her running mate, Minnesota’s governor, Tim Walz, continued their swing-state tour with rallies in rural Wisconsin and Detroit, Michigan, on Wednesday, that the campaign said brought out more than 10,000 people each.

The rallies, which followed a raucous event in Philadelphia, served as an opportunity for Harris to continue to introduce Walz, a formerly low-profile midwest governor, to Democrats in the critical swing state.

In Eau Claire, a north-western Wisconsin city less than two hours from Minneapolis and St Paul, Minnesota, the rally drew attendees from both states – and 12,000 people in total, the campaign said. The Detroit rally on Wednesday night drew 15,000 supporters in another crucial swing state, the Harris campaign told reporters. Walz called it “the largest rally of the campaign” so far.

The big Detroit crowd repeatedly chanted: “We’re not going back,” Democrats’ counter to Trump’s anti-abortion politics and “make America great again” slogan.

Attendees in Wisconsin said they were enthusiastic to see a Harris and Walz ticket. “I’m elated,” said Lori Schlecht, a teacher from Minnesota who said she is excited about Walz given his background in public education – Walz was a public school teacher before he was elected to the US House of Representatives in 2006. “Minnesota is blessed to have him, and I’m glad to see him at the national level. He is authentic and real – he’ll get shit done.”

Many Minnesota residents in attendance pointed to Walz’s down-to-earth manner as an asset to the Democratic party ticket.

“Walz is my homeboy,” said Colin Mgam, who is 65 and retired and drove from St Paul for the rally. “He brings straight talk, and he’s going to do well,” Mgam added.

As midwestern Democrats praised Walz as “one of us”, the Harris campaign announced Wednesday that it had raised $36m from supporters in the 24 hours since it announced him as Harris’s running mate.

The rallies did see some shaky moments, with protesters in the Detroit crowd briefly trying to disrupt Harris’s speech. Reporters on the scene said the interruption came from pro-Palestinian protesters chanting: “Kamala, Kamala, you can’t hide. We won’t vote for genocide.”

In response, Harris first said that in a democracy, everyone’s voice matters, but that “I am speaking now.” Then, as the shouts from protesters continued, she said: “You know what? If you want Donald Trump to win, then say that, otherwise I’m speaking.” The crowd cheered.

Both rallies were also marked by medical incidents as thousands of people stood together packed in the summer heat, prompting several speakers to pause their remarks and flag that people in the crowd needed assistance. Calls for a “medic” interrupted multiple speeches, including both of Walz’s. In Wisconsin, Walz urged supporters to drink water and “take care of one another”. In Michigan, he thanked the crowd for taking care of their neighbors. “We are neighbors, and we’re not weird,” he said.

The Eau Claire rally highlighted Harris’s focus on Wisconsin, where she held her first rally after Joe Biden announced the end of his bid for re-election. In 2016, Donald Trump won Wisconsin by about 20,000 votes, and Biden won the state in 2020 by a similar margin.

The indie folk band Bon Iver, whose lead singer is from Eau Claire and previously supported Bernie Sanders’ 2016 and 2020 presidential campaigns, opened for Harris at the Wednesday event.

In Wisconsin, Walz spoke first, focusing on his midwestern background and noting he had family in the crowd. “Being a midwesterner, I know something about commitment to the people,” he said. He also spoke at length about his experience coaching football, teaching social studies and serving in the Minnesota National Guard, underscoring his role as a kind of ambassador to rural and working-class Americans for the Democratic party.

And he directly took on Trump. “Don’t believe him when he plays dumb. He knows exactly what he’s talking about. He knows exactly what Project 2025 will do in restricting and taking our freedoms. He knows that it rigs the economy for the super rich if he gets a chance to go back to the White House. It will be far worse than it was four years ago.”

Walz also revisited his support for and personal experience with IVF, the fertility treatment, which has become a contentious issue for Republicans after an Alabama court ruled that frozen embryos have personhood.

In Michigan, Harris reiterated her now-popular attack line that, as a prosecutor, she “knows Donald Trump’s type”, but had to cut off her supporters’ repeated chants of “Lock him up!” when she talked about Trump’s recent convictions, telling them that the courts will handle that, and that “we are going to beat him in November.”

United Auto Workers president Shawn Fain, who appeared on stage before Harris in Detroit, called her “a badass woman who stood on the picket line with striking workers” and praised Walz one of the union’s top picks for vice-president.

“He’s one of us. He’s a working class guy. He knows working class values,” Fain said. “Best of all, he’s a proud union member.”

Fain called Trump “a lapdog for the billionaire class” and “a scab”, prompting the Detroit crowd to chant: “He’s a scab! He’s a scab!”

Walz, who was not initially an obvious contender for Harris’s vice-presidential pick, garnered widespread attention within the party after giving a candid and upbeat interview on MSNBC’s Morning Joe in which he boosted Harris and wrote off Donald Trump’s running mate JD Vance as “weird”.

Donald Trump has been quick to paint Walz, who has worked with progressive lawmakers in Minnesota to pass a raft of progressive laws – codifying the right to abortion, expanding protections for workers and establishing landmark voting rights legislation – as a member of the “radical left”, a line of attack that the former president will likely continue to push.

But Walz pushed back against Trump on Wednesday in Wisconsin. “This election is all about asking that question, which direction will this country go in? Donald Trump knows the direction he wants to take it. He wants to take us back.”