Washington (AFP) - Former US president Barack Obama will lend some star power to Kamala Harris’s campaign in the must-win swing state of Pennsylvania Thursday as Democrats struggle to move the dial against Donald Trump.

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

Harris will head to yet more swing states, Nevada and Arizona, to reach out to Latino voters, but the White House said the vice president had also taken part in a virtual briefing on 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’s campaign also bashed Harris on the economy after US consumer inflation cooled last month, though slightly less than expected. High prices for Americans are one of the biggest issues in the election.

“Kamala Harris’s terrible economic policies continue to hit the American people where it hurts,” spokeswoman Karoline Leavitt said in a statement.

In a sign of Pennsylvania’s critical importance to the White House race, Trump rallied there on Wednesday in Biden’s childhood hometown of Scranton. He is heading on Thursday to the auto industry capital of Detroit in Michigan, another battleground.

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, 63 – who was in the White House from 2009 to 2017 before Trump’s single 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, 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 is expected to talk about the “enormous stakes” of the election and push the “critical early vote period in Pennsylvania,” it said.

Democrats have historically favored early voting over Republicans.

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

The Republican himself has also sometimes called early voting into question, despite efforts by his campaign to promote it.

Obama remains hugely influential in the Democratic party and endorsed Harris, 59, after Biden dropped out of the race in July.

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.”

The ex-president has also pulled in more than $76 million for the Democratic ticket in this year’s presidential race.

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