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California Gov. Gavin Newsom responded to former President Donald Trump facing federal indictment for the alleged mishandling of classified documents in an exclusive interview with Fox News' Sean Hannity.

Newsom, who has not held back in his critiques of other top Republicans like Florida Gov. Ron DeSantis, said he was saddened by the 2024 Republican front-runner's scheduled trial in Miami.

"It was sad – and I say that as an American," Newsom said in an interview that aired Monday on "Hannity."

Hannity asked what his relationship was like with Trump when he was in the White House.

Former President Donald Trump, center, Florida Gov. Ron DeSantis, right, and California Gov. Gavin Newsom, left

Former President Donald Trump, center, Florida Gov. Ron DeSantis, right, and California Gov. Gavin Newsom, left (Getty Images)

Newsom said the two engaged in a politically-unique cooperation during the coronavirus pandemic, with the-top Democratic governor praising Trump.

"I didn't have a closed fist, I had an open hand. We actually had an incredible relationship during COVID," Newsom said.

"He was incredible – he played no politics during COVID with California – none whatsoever. It's a fact."

The governor said that some in his own party criticized him for declining to attack Trump during the pandemic.

Newsom also was asked about the publication of photographs showing him and his wife Jennifer dining at the upscale French Laundry restaurant while businesses in his and many other blue states were placed under hefty restrictions.

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Former President Donald Trump arrives at Trump Tower

Trump (AP Photo/Yuki Iwamura)

At the time, Newsom had enacted tough restrictions, like forced shuttering of indoor dining in many of the state's counties. The French Laundry dinner was a 50th birthday celebration for a political adviser.

A spokesperson for the adviser told FOX's Los Angeles affiliate the meal setup was considered "outdoors."

"It was a dumb – it was a terrible mistake," Newsom told Hannity. "It wasn't illegal, it was wrong. And I totally violated the spirit of what I was preaching. And it was wrong. And I own that."

He also doubled down on his plan to appoint an African-American woman to the U.S. Senate if the replacement of Sen. Dianne Feinstein, D-Calif., falls in his lap.

Feinstein, 89 and serving since 1992, developed severe complications from shingles earlier this year, raising questions about her ability to finish her term. 

Speculation about who will succeed Feinstein, whether she decides to finish her term or not, has led to varied reports. Some speculate whether there is significance that a daughter of Rep. Nancy Pelosi, D-Calif., has been aiding the senator in order to help prospective successor Rep. Adam Schiff., D-Calif.

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A spokesperson for Pelosi responded "no" to a May inquiry by Fox News Digital whether Pelosi's daughter's, also named Nancy, arrangement is intended to help Schiff's campaign.

Separately, Rep. Barbara Lee, D-Calif., who is Black, has said she would accept an appointment from Newsom if offered, according to a report from California's KQED radio.

Hannity asked Newsom why he has set such parameters for a Senate appointment, versus basing one solely on merit.

"We lost with the Kamala Harris. We lost that representation. It's important. It's historic. I appointed the first Latino in California's history – [a race that makes up] 39% of the state. I thought that was important," Newsom replied.

In another part of the interview, Newsom said he would readily accept an invitation for a Hannity-moderated issues-based debate with DeSantis.

More of Sean Hannity's exclusive interview with Gov, Newsom will air on "Hannity" later this week.

Fox News' Elizabeth Elkind contributed to this report.