West Virginia Sen. Joe Manchin wrote in a statement on X that "I can think of no one better than Governor Walz to help bring our country closer together and bring balance back to the Democratic Party."

"My friend Governor Tim Walz will bring normality back to the most chaotic political environment that most of us have ever seen," he said, in part, also calling him "the real deal."

-ABC News' Lauren Peller

Independent presidential candidate Robert F. Kennedy Jr. wrote on X that Minnesota Gov. Tim Walz being picked as Harris' running mate means that "America's political divide sharpens."

"He called Trump supporters 'fascist' and 'weird,' and they in turn are calling him worse than that," he said.

-ABC News' Oren Oppenheim

Minnesota Sen. Amy Klobuchar spoke to ABC News Live about her reaction Gov. Tim Walz being selected as Vice President Kamala Harris' running mate.

The senator called Walz a "close friend," and said Harris chose the governor for several major reasons.

"She had someone in Tim Walz that one, she trusted, [and] two, she saw as someone that is going to bring something else to this ticket in a big way," Klobuchar said.

The senator said Walz's experiences as a veteran, teacher, Congress member and governor help the ticket.

"I just like Tim Walz. He is a good leader, he has shown he can get things done across the aisle," she said.

When asked about the criticism Walz received over his handling of the COVID-19 pandemic, Klobuchar said, "We came out of it strong."

Klobuchar also addressed the criticism Walz received over the 2020 George Floyd protests, reiterating that the governor embraced peaceful protests but called in the National Guard when they got violent.

"I would like to add, he was someone when the 'defund the police' ballot measure was on the ballot in the city of Minneapolis, both of us strongly opposed the measure. He added funding for the police," she said. "You will see someone who has actually stood with law enforcement and made some tough decisions."

Republican vice presidential nominee Sen. JD Vance responded to the news of Gov. Tim Walz being tapped as Kamala Harris' running mate, claiming the decision highlights how "radical" Harris is.

"Obviously, the big news of the day is that Tim Walz has been nominated as the VP or is now the presumptive nominee, I should say, for Kamala Harris ... My view on it is it just highlights how radical Kamala Harris is," Vance said.

When asked by ABC News' Hannah Demissie if he had been in contact with Walz, Vance said he called Walz but the governor didn't answer, so he left a voicemail.

"I didn't get him, but I just said, 'Look, congratulations. Look forward to a robust conversation and enjoy the ride,' And maybe he'll call me back, maybe he won't," Vance said.

-ABC News Lalee Ibssa