Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE (R-Ariz.) said he regrets choosing former Alaska Gov. Sarah Palin (R) to be his running mate during the 2008 presidential campaign.

The New York Times reported on Saturday that McCain, while still defending Palin’s performance, said in his upcoming book, “The Restless Wave: Good Times, Just Causes, Great Fights, and other Appreciations,” that he wishes he had instead selected former Sen. Joseph Lieberman (I-Conn.)

His advisers reportedly had warned against choosing Lieberman, who was once a Democrat, stating that Lieberman’s support of abortion rights could divide Republicans.

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“It was sound advice that I could reason for myself,” he writes. “But my gut told me to ignore it and I wish I had.”

In a new HBO documentary, McCain goes on to say that not choosing Lieberman was “another mistake" that he made in his political career.

Lieberman told the Times that he didn’t know McCain felt that way.

“It touched me greatly,” he said of the film.

The Times reported that Lieberman recently visited McCain, 81, at his ranch in Arizona where the senator is recovering from his brain cancer treatment and surgery for an infection.

Recently released excerpts from McCain’s upcoming memoir indicate that he doesn’t know how much time he has left to live while battling the glioblastoma he was diagnosed with last year.

Although the memoir isn’t entirely political, McCain still takes swings at President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE.

McCain writes that the president seems to care more about “the appearance of toughness” than American values, chiding Trump's coziness with Russian President Vladimir Putin, in particular.

“The Restless Wave: Good Times, Just Causes, Great Fights, and other Appreciations” will be released May 22.