Pittsburgh (AFP) - Former US president Barack Obama will lend some star power to Kamala Harris’s campaign Thursday in the must-win swing state of Pennsylvania, as Democrats fight to move the dial against Donald Trump just weeks before Election Day.

America’s first Black president will lead a rally in the steel city of Pittsburgh, his first stop on a tour of battleground states, to urge people to cast early votes for November’s nail-biting election.

Harris was in battleground Nevada for a town hall Thursday and heads to Arizona Friday to reach out to Latino voters. But the White House said the vice president had also taken part in a virtual briefing on deadly Hurricane Milton, which crashed into Florida overnight.

Republican former president Trump stepped up his criticisms of Harris and President Joe Biden over their response to the hurricane – attacks that Biden has branded an “onslaught of lies.”

“Hopefully on January 20 you’re going to have somebody who’s really going to help you,” Trump said in a video message to the people of Florida, where he lives.

Trump was in the hotly contested state of Michigan on Thursday, unveiling new details of his protectionist plans for the US auto industry, including sweeping tariffs on vehicles not made in America.

European manufacturers “send their cars to us, like a bunch of dummies we are… by the millions and millions and millions,” he said in the auto industry capital Detroit.

“We’re not doing that crap anymore, OK? Now they’re going to have to play by our rules.”

Trump, in comments that sounded increasingly menacing, also ramped up his personal attacks on Harris, branding her “dumber than hell,” and assailed Detroit itself as run down as he was speaking to the city’s economic club.

“Our whole country will end up being like Detroit if she’s your president.”

Trump bashed Harris on the economy even after US consumer inflation cooled last month, though slightly less than expected, saying she and Biden have presided over an “inflation disaster.”

High prices for Americans are one of the biggest issues in the election.

Harris meanwhile said she had accepted an offer for a CNN town hall on October 23 in Pennsylvania, after Trump turned down a final televised debate with her.

- ‘All hands on deck’ -

Democrats are hoping Obama – who was in the White House from 2009 to 2017 before Trump’s term – could give Harris a boost in a race that remains neck-and-neck.

Despite an initial surge in the polls after she dramatically replaced Biden as Democratic nominee in July, and a reported $1 billion in fundraising, Harris and Trump are still effectively tied nationwide and in swing states.

“President Obama believes this is an all hands on deck moment which is why he’ll be doing everything he can to help elect vice president Harris,” his office said.

Obama, 63, is expected to speak in Pittsburgh at 7:15 pm (2315 GMT). He will likely talk about the “enormous stakes” of the election and push the “critical early vote period in Pennsylvania,” his office added.

Democrats have historically favored early voting over Republicans.

Trump has meanwhile frequently lashed out against anything except actual election day voting, repeatedly blaming mail-in ballots for his 2020 defeat by Biden.

Obama remains hugely influential in the Democratic Party and quickly endorsed Harris, 59, after Biden ended his reelection bid.

Obama and former first lady Michelle Obama delivered rapturously received speeches backing Harris at the Democratic National Convention in August.

He portrayed Harris – America’s first woman, Black and South Asian vice president – as the political heir to his own trailblazing path.

Obama led the crowd in chants of “Yes, she can” – a riff on the “Yes, we can” chants from his own 2008 campaign – but warned that 2024 would “still be a tight race in a closely divided country.”

Former president Bill Clinton is also expected to hit battleground states in coming days to campaign for Harris, CNN reported.