Kamala Harris rallied supporters in the swing state of Wisconsin on Thursday, October 17 while Donald Trump stirred controversy with criticism of embattled ally Ukraine, as the rivals vied for the remaining undecided voters in a deadlocked US presidential election.

The candidates are racing toward Election Day on November 5 with the Democratic vice president narrowly leading her Republican rival nationally and in several crucial swing states, although most polls are within the margin of error. Both are also deploying high-profile surrogates to sew up support in the race's final weeks, including billionaire Elon Musk's series of appearances for Trump in must-win Pennsylvania.

Harris worked a crowd in the manufacturing hub of La Crosse, Wisconsin, saying "We are nearing the home stretch, and this is going to be a tight race until the very end."

"Donald Trump is an unserious man, and the consequences of him ever getting his foot back in the Oval Office are brutally serious," she later said.

Harris, who also rallied voters in Green Bay, one of Wisconsin's largest cities, extending her outreach to the state's young voters and blue-collar workers.

'Fate of America'

Trump, meanwhile, sat for an interview with a supportive podcast, dominated by immigration, the economy and his grievances against the US media -- although he made news by blaming Ukraine's President Volodymyr Zelensky for Russia's invasion of his country.

"Zelensky is one of the greatest salesmen I've ever seen. Every time he comes in, we give him $100 billion. Who else got that kind of money in history? There's never been (anyone)," Trump told the two-million-subscriber PBD Podcast. "And that doesn't mean I don't want to help him, because I feel very badly for those people. He should never have let that war start."

The Trump campaign claimed he had been talking about President Joe Biden, but his remarks were widely interpreted as a swipe at Ukraine.

At the same time, Elon Musk's increasingly visible role in Trump's campaign included the billionaire launching five nights of campaign events in Pennsylvania. "This election, I think, is going to decide the fate of America and, along with the fate of America, the fate of Western civilization," he said at a town hall event in Folsom, on the outskirts of Philadelphia.

Harris on Thursday addressed her decision to appear on Fox, telling the crowd in La Crosse she wanted to represent all Americans "no matter their political party, where they live or where they get their news."