Joe Biden’s camp wouldn’t have been surprised to hear a Bernie Sanders booster say (on Bernie’s 2020-primary YouTube channel) that the former veep “has basically been on the wrong side of almost every significant issue in essentially my lifetime” — except for the fact that the booster in question had either asked to work for Biden, discussed working for him or tried to secure his support on several occasions over several years.

As she writes in her book “Reversing The Apocalypse,” in 2015 “Hill TV” host and former MSNBC talking head Krystal Ball was so keen to land work for Biden’s much anticipated 2016 White House campaign that she moved her family into temporary housing in Washington, DC, just in case he ran. (He didn’t, of course.)

Meanwhile, insiders say that in 2017, Ball and Biden’s camp once again discussed plans for Ball to join the team, this time drafting ideas for his institute. (We’re told that they approached her on that occasion, and ultimately she didn’t sign up to do that work). And then in 2018 Ball asked Biden’s team to consider endorsing a raft of candidates she was backing in the midterms, lauding his appeal in key districts. A source close to Ball told us, “Of course Krystal tried to get endorsements for her candidates. It would have been political malpractice not to!”

A source told us that it’s common for aides to move between candidates, but that insiders had been shocked by how extreme Ball’s criticism of Biden had become, considering how eager she had been to work with the Biden campaign “from the ground up.”

Ball told us of her 2015 approach to work on the Biden campaign, “At the time, he was planning to run to Hillary’s left and I thought that was important.” She added, “This time around he has instead decided to position himself to the party’s right. I am not endorsing any candidate because that is not my role as the progressive host on Hill.tv. But there is absolutely no doubt that I ­believe 2020 is a different moment than 2016.”