There wouldn’t be new primaries. Biden’s pledged delegates would be released to do whatever they want. Obviously that has its own share of, small d, democratic concerns, but the better choice if you ask me.

https://www.nytimes.com/2024/06/28/us/politics/replace-biden.html?unlocked_article_code=1.3E0.F9in.hk_iHLn0B5pI&smid=nytcore-ios-share&referringSource=articleShare&sgrp=c-cb