WASHINGTON — Former President Barack Obama was scheduled to headline a rally Thursday night in the battleground state of Pennsylvania, as Vice President Kamala Harris’ campaign seeks to use one of her party’s most popular politicians to mobilize the Democratic base.

Meanwhile, Donald Trump on Thursday again complained about the federal response to natural disasters that have damaged much of the Southeast as he seeks to gain a political advantage from the tropical weather.

The former president spoke at the Detroit Economic Club after holding rallies Wednesday in Pennsylvania.

Trump sent a message to people affected by Hurricane Milton and Hurricane Helene. He praised Republican governors of Florida, Georgia and South Carolina but suggested the federal response had been lacking, particularly in North Carolina, where he alleged the government after Helene had “not done what you’re supposed to be doing.”

“They’ve let those people suffer unjustly,” said Trump, who has for several days promoted falsehoods about the response of President Joe Biden and emergency management officials.

Speaking Thursday at the White House, Biden condemned the “reckless, irresponsible and relentless disinformation and outright lies that continue to flow.” He publicly admonished Trump, telling his predecessor to “get a life, man” and try to help people affected by a pair of devastating hurricanes rather than spreading misinformation about the federal response.

For Harris, unleashing Obama is a sign that her campaign is moving into its highest gear with Election Day less than a month away and the presidential race exceedingly close. This week, her operation is turning its focus from fundraising and defining her message to getting out the vote as quickly as possible.

Obama’s rally Thursday in Pittsburgh kick-starts that effort. And he is expected to continue rallying Democrats to the polls in several more battleground state events in the coming weeks.

“You bring in someone like Barack Obama to inspire people, to encourage them to participate and to set the stakes and urge them to vote,” said David Axelrod, a former strategist for Obama. “There’s no one better.”

Encouraging early voting is a key campaign strategy. As more Democrats cast their ballots early, it becomes easier for the Harris campaign to find and turn out the voters who are harder to reach.

Early voting has already begun in Pennsylvania, which Harris must almost certainly win to defeat former President Donald Trump. She holds a narrow lead in the polls there, having overcome the significant deficit she inherited from President Joe Biden. Democrats are hoping for high voter turnout in the state’s biggest cities, Pittsburgh and Philadelphia.

But there are some worrying signs: Harris’ support among Black voters, for instance, is still lower than what Biden received when he won the state in 2020, according to a poll last month from The New York Times, The Philadelphia Inquirer and Siena College.

Black men in particular have been a weak point for Harris, and the vocal support of Obama, the first Black president, could help her there.

“He’s the biggest gun that Democrats have in their arsenal,” said Cornell Belcher, a Democratic pollster who worked on Obama’s presidential campaigns. “And here at the close, you’ve got to use the biggest gun you’ve got.”

Obama remains adored by Democrats, making him a natural surrogate for Harris on the campaign trail. More than 90% of Democrats and many independents view him favorably, according to an August survey by The Economist and YouGov — well above other Democrats, including Biden, Bill Clinton and Hillary Clinton.

“They’ve got to release the kraken,” said James Carville, a veteran Democratic strategist, adding that the Harris campaign should be using Obama and other high-profile surrogates more aggressively. “He’s got, obviously, tremendous appeal to Black voters. He has tremendous appeal to suburban whites, which is another big part of the coalition. And he drives Trump nuts.”

In addition to campaigning for the top of the ticket, Obama is trying to help down-ballot candidates. Democrats running for Senate in Florida, Maryland, Michigan and Nevada have released ads featuring him. On Thursday, he is expected to also make a push for Sen. Bob Casey of Pennsylvania, who is running for reelection.

Associated Press contributed.