HOUSTON (AP) — Vice President Kamala Harris is slated to continue her days-old presidential push by speaking Thursday to the American Federation of Teachers, the first labor union to formally endorse her candidacy.

Having emerged as the likely Democratic nominee after President Joe Biden exited the race, Harris plans to travel aggressively to spread her message and rally voters. The outreach occurs as the former and retooled Biden campaign, now under Harris’ control, figures out its strategy for generating turnout and maximizing her time in a 100-plus day sprint to the November election against Republican Donald Trump.

But in Trump, Harris is up against the survivor of a recent assassination attempt with tens of millions of loyalists who are devoted to putting him back in the Oval Office. Just as Harris is trying to draw a contrast with Trump, he is trying to do the same with her.

Trump went on the offensive against Harris at a Wednesday rally in North Carolina, telling his crowd of thousands that she is a “real liberal” who is “much worse” than Biden. The former president said Harris had misled voters about the health of the 81-year old Biden and his ability to run for the presidency.

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“For three and a half years, Harris shamelessly lied to the public to cover up Joe Biden’s mental unfitness, claiming that ‘crooked Joe’ was at the absolute top of his game,” Trump said. “I don’t think so. I don’t think so.”

The vice president’s address at the union’s biennial convention in Houston follows a Tuesday rally in the Milwaukee area and a Wednesday speech to a gathering of the historically Black sorority Zeta Phi Beta in Indianapolis.

“We know when we organize, mountains move,” she told the thousands of sorority members on Wednesday. “When we mobilize, nations change. And when we vote, we make history.”

The 1.8 million-member AFT has backed Harris and her pro-union agenda on the premise that a Trump return to the White House could result in restrictions on organized labor and a potential loss of funding for education.

Randi Weingarten, the union’s president, posted on social media ahead of Harris’ appearance, “We are fully committed to this fight: united, mobilized and ready to vote in this year’s election.”

The AFL-CIO, which represents 60 labor unions including the AFT, has backed Harris. But the vice president has yet to get the endorsement of the United Auto Workers, with its president Shawn Fain telling CNBC in a Monday interview that the decision will be made by his union’s executive board.

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Fain spoke at the AFT conference on Wednesday and was blistering in his criticism of Trump. The former president has relied on blue-collar voters to compete politically nationwide, but he failed to win a majority of union households in 2020 and lost to Biden, according to AP VoteCast.

“It’s very clear a Donald Trump White House would be a disaster for the working class,” Fain said. “Donald Trump is a scab. He stands for everything that we as union and in the labor movement stand against.”

After her speech, Harris will return to Washington and meet in the afternoon with Israeli Prime Minister Benjamin Netanyahu.