What a scumbag. I don’t think I’ve ever heard any other candidate — Democrat or Republican — say that they regretted their vice presidential pick. Its just plain low.
I believe Tom Dewey later said that he regretted choosing Governor Earl Warren of CA in 1948. Warren could not hold CA for Dewey, but John Bricker in 1944 held OH for Dewey.
More than a swipe at Palin this is one of his last strikes (like a rattlesnake) at conservatives. He was always a dim at heart and conservatives were always hated by him. He always had to run as a conservative to get elected and has a lot of anger that conservatives have any power. He has only thinly covered that up over the many years. I think Trump being elected, by conservatives angered him as much as any of the in your face lefties. He has far more in common with them than us.