Former Vice President Mike Pence reiterated Friday that he would not vote for his successor despite not supporting former President Donald Trump.

"Let me go on the record here at the gathering: I could never vote for Kamala Harris as president of the United States, or Tim Walz, as her running mate. Period," Pence said during an on-camera interview with conservative radio host Erick Erickson.

Pence defended his decision to not support Trump, citing several issues including "marginalizing the right-to-life in our party, as we saw on the national platform."

"I cannot endorse President Trump's continuing assertion that I should have set aside my oath to support and defend the Constitution and acted in a way that would have overturned the election in January of 2021," Pence added.

The former vice president did say he was grateful that Trump was not seriously hurt during the attempted assassination during a rally in Pennsylvania last month.

"Karen and I, we were in a plane, we had just landed, and I had got a text from someone watching it in real time. It took my breath away," he said, referring to his wife. "I truly admired the way the president stood up and raised his fist and walked off that stage."

-ABC News' Brittany Shepherd

President Biden and Vice President Harris will hold a joint event in Maryland on Thursday, Aug. 15, according to the White House.

They will discuss "the progress they are making to lower costs for the American people," the White House said.

Meanwhile, ahead of visits this weekend to Arizona and Nevada, the Harris campaign is touting what it called its "historic ground game advantage" in the two battleground states.

In a memo, the campaign also notes the elevated importance in Arizona and Nevada of reproductive freedom, as abortion-related ballot measures will be in place in each state this fall.

"Vice President Kamala Harris and Governor Tim Walz's momentum across the battlegrounds is real and will be on full display in Arizona and Nevada, where we've built massive coordinated campaigns as Trump has almost no presence whatsoever," the memo read. "Our campaign will continue our work to reach the diverse voters who power our victories in the Southwest, highlighting the stakes of the race for reproductive rights and the Vice President's leadership to secure the border."

Former President Donald Trump is set to hold a campaign rally in Bozeman, Montana, on Friday.

Vice President Kamala Harris will not be joining former President Donald Trump on Fox News' debate stage on Sept. 4, a Harris campaign official told ABC News.

The official said Harris agreeing to future debates is contingent on Trump showing up and "keeping his word" to the Sept. 10 debate, hosted by ABC News.

Harris' campaign is willing to have conversations about future debates, but they must be scheduled after Sept. 10, according to the official.

Vice President Kamala Harris and Gov. Tim Walz gave remarks at a local United Auto Workers office in Wayne, Michigan, on Thursday, championing "the collective."

Walz praised Harris' leadership, saying, "She stands on the side of the American people and the American worker. She’s the one who took on the predators, the fraudsters, the transnational gangs," Walz said.

"And she’s the one that stands up against the billionaires and the corporate greed -- it’s who Kamala Harris is," he added.

Harris took the stage largely repeating her newly tested stump speech, letting the audience know her campaign is for everyone.

"We believe in the collective," Harris said. "We're not falling for these folks who are trying to divide us trying to separate us, trying to pull us apart. That's not where the strength lies," she added.

She ended her remarks by reminding the crowd of how many days were left until voting day and how much hard work was left to win the election.

"We've got 89 days to get this done. You know, the one thing about all of us is we like hard work. Hard work is good work," she said.

-ABC News' Gabriella Abdul-hakim