Election 2024 updates: Gov. Andy Beshear says JD Vance 'ain't from Appalachia' while campaigning for Harris

Ahead of Vice President Kamala Harris' speech at the American Federation of Teachers (AFT) national convention, AFT President Randi Weingarten and National Education Association President Becky Pringle both endorsed Harris for president.

"Vice President Harris has delivered time and again for students and educators, and educators know we can count on her continued partnership in expanding access to free school meals for students, investing in student mental health, working to ensure no educator has to carry the weight of crushing student debt and, doing everything possible to keep our communities and schools safe," Pringle said in a statement Tuesday.

Harris is expected to give a keynote address this week at the AFT convention in Houston, on Thursday. She will be speaking to the nation's largest teachers union at their 88th annual gathering.

ABC News' Arthur Jones II

Former Secretary of State Hillary Clinton published an op-ed in the New York Times on Tuesday reaffirming her support of Harris and warning of the attacks that Republicans will use against her during the campaign.

The 2016 Democratic nominee said that Harris is "chronically underestimated, as are so many women in politics, but she is well prepared for this moment," citing the vice president's experience as a prosecutor, U.S. senator and four years in the White House.

"Harris has sat with the president in the Situation Room, helping make the hardest decisions a leader can make. And when the extremist Supreme Court overturned Roe v. Wade, she became the administration’s most passionate and effective advocate for restoring women’s reproductive rights," Clinton wrote.

Clinton referred to her own candidacy and the sexist attacks labeled against her by Republicans and critics. She said Harris "will face unique additional challenges as the first Black and South Asian woman to be at the top of a major party’s ticket."

"Ms. Harris’s record and character will be distorted and disparaged by a flood of disinformation and the kind of ugly prejudice we’re already hearing from MAGA mouthpieces. She and the campaign will have to cut through the noise, and all of us as voters must be thoughtful about what we read, believe and share," Clinton said.

Arizona Sen. Mark Kelly dodged questions from an ABC News reporter Tuesday about whether he received vetting materials for a potential vice presidential ticket.

"This is not about me," he said. "I'm going to be focused on doing everything I can to make sure she is elected because we cannot have a repeat of what we saw between 2016 and 2020."

Kelly is seen as one of the front-runners to be Vice President Harris' running mate, sources have told ABC News.

-ABC News' Allison Pecorin

Harris is scheduled to visit Houston on Thursday to deliver the keynote speech at the American Federation of Teachers’ 88th national convention, according to the campaign.

"The Vice President’s speech to educators from communities throughout the nation is a continuation of her consistent efforts to fight for workers across America, including as Chair of the White House Task Force on Worker Organizing and Empowerment," the campaign said in a statement.

-ABC News' Cheyenne Haslett