Biden, in political crisis, holds campaign rally in Wisconsin ahead of pivotal ABC News interview

President Joe Biden heads to 2024 battleground Wisconsin on Friday for a closely-watched campaign rally and a critical interview with ABC News that could prove pivotal to his candidacy and presidency.

Biden is under growing pressure from some Democrats to publicly prove his mental and physical fitness -- by answering questions and making unscripted remarks -- and he'll get a high-stakes chance to do so when ABC anchor George Stephanopoulos speaks with him in Madison, Wisconsin, on Friday.

The first excerpts will air on "World News Tonight" and then the interview will be broadcast in its entirety in a prime-time ABC network special on Friday evening at 8 p.m. ET.

Watch: ABC News anchor George Stephanopoulos' exclusive first post-debate TV interview with President Joe Biden airs in its entirety in an ABC News prime-time special Friday, July 5, at 8 p.m. ET.

"I'm not going anywhere," Biden said Thursday, speaking at a July Fourth barbecue for military families when someone in the crowd shouted, "Keep up the fight."

Meeting with Democratic governors at the White House Wednesday to address their urgent concerns following his disastrous debate performance, Biden vowed to continue his presidential campaign, according to California Gov. Gavin Newsom.

One of more than 20 Democratic governors who met behind closed doors with Biden – virtually as well as in-person -- Newsom said Thursday while campaigning for Biden in Michigan, "I was really proud to be with Joe Biden last night. He started the meeting -- the first words out of his mouth: "I'm all in." And when we left that meeting, convinced ... there was no one that walked out of that and didn't say, 'We've got your back, Mr. President.' No one. Not on."

Another Democrat who's been speculated about as a possible replacement as the party's nominee, Michigan Gov. Gretchen Whitmer, posted, "Joe Biden is our nominee. He is in it to win it and I support him."

At the same time, though, more than a half dozen governors in the meeting expressed concern over the president's debate performance and the resulting fallout inside the party, two people familiar with the conversation told ABC News Senior Congressional Correspondent Rachel Scott.

According to those people, one governor told Biden flat-out that people didn't think he was up to the task of running, and another asked him to lay out the path forward.

One person who attended the meeting described the conversation as "candid" and "blunt," saying the president was "engaged" and "focused."

Meanwhile, some congressional Democrats have gone public with their calls for Biden to step aside.

After Texas Rep. Lloyd Doggett on Tuesday became the first lawmaker to publicly say Biden should leave the race, another House Democrat -- Rep. Seth Moulton of Massachusetts -- said Thursday that Biden should withdraw.

"President Biden has done enormous service to our country, but now is the time for him to follow in one of our founding father, George Washington's footsteps and step aside to let new leaders rise up and run against Donald Trump," Moulton told WBUR.

Rep. Raúl M. Grijalva of Arizona publicly urged Biden to leave the race, citing the "precarious" state of the president's campaign in an interview with The New York Times. He voiced concerns about Biden dragging down House Democrats with him in November.

Rep. Marie Gluesenkamp Perez of Washington state told KATU she thinks Biden's performance last Thursday will cost him the election against former President Donald Trump.

"Biden's going to lose to Trump. I know that's difficult, but I think the damage has been done by that debate," she said.

As part of his effort to reassure Democrats and the American public, Biden did an interview with a prominent Black radio host, Earl Ingram of CivicMedia, whose Wisconsin-based program is aimed at Black listeners, a critical voting bloc in a state where just a few thousand votes could help decide the election.

Biden said he had "made a mistake" at the debate in the exchange that aired Thursday.

"I had a bad night. I had a bad night. And the fact of the matter is that, you know, it was -- I, I, I screwed up, I made a mistake, and but I learned from my father, when you get knocked down, you just get back up," he said.

"Look I came back from, I -- I didn't have a good debate. That's 90 minutes on stage. Look at what I've done in 3.5 years," he added.

ABC News' Molly Nagle, Cheyenne Haslett, Isabella Murray and Oren Oppenheim contributed to this report.