Since we’ve moved to a larger discussion on primary challengers rather than just Cenk, I want to pause for a moment to bring up the elephant in the room: Trump.
@Mijin has been passionately making the point that in a functioning Democracy, a qualified challenger has every right to go against an incumbent if they can do a better job of running the party or the nation. This isn’t wrong.
BUT
That’s not what Cenk is/was doing according to the OP. They were stating that Biden is weak and that others (including themselves, but not limited to themselves) could or should do a better job.
Campaigning on the weakness of the leading candidate (leaving out entirely the debate on whether said weakness is real or imagined) DOES damage that candidate if they win the primary, whether or not that’s the intent.
Unless (as we see on the Republican side) the cult (of personality or otherwise) is so entrenched that any weakness, verifiable real (90+ indictments) or imagined is hand-waved as an alternate reality. Biden is a far better person than Trump (yes, I know, drastic understatement), but doesn’t command an unquestioning base.
If we WEREN’T in a situation of a post-Trump world with the SCOTUS corruptly (but legally!) unbalanced, the Republican party overtaken by nihilists, multiple escalating world events that we’re increasingly too paralyzed to deal with due to internal division, and with the strong possibility of the enabler of all the above (not source, but enabler) being granted a position of supreme executive power… I’d be willing to give @Mijin’s world of ideals over practicality a chance.
For example, if this was 2008 or 2012 and we were running against McCain or even Romney, we’d be in a position where I’d be unhappy with the results, but wouldn’t doubt the sanity or the safety of the nation if they won. I would just wish the Democratic candidate had done better. Heck, talking about 2008, there was a feeling that Obama was a spoiler of sorts, and it should have been Hillary instead.
But it’s 2024. The other side is Trump. I firmly doubt the sanity of Trump, and equally so the safety of the nation (at least, as a democratic one) if he wins. Trump has the advantage of a nearly unified propaganda machine, a supine party, and a willingness to throw Democracy under the bus as long as he gets what he wants.
Right now, an ideal candidate is the one that beats Trump. Biden, of all the current options, is the closest to that ideal. Do I wish we had a younger candidate? Sure do. Do I wish sometimes that he’d fight back at Trump’s level? Emotionally, sure, but playing the game the other guy is good at isn’t a winning option either.
And sure, I know a lot of people are further left than me politically and would want a candidate closer to their preferences, but that’s a known issue with a (compared to Republicans/MAGA) broad tent.
Absolutely though, even if the Democrats win in 2024 ( 
) the party absolutely has to work on messaging, and build the bench as it were. We need more of Jeffries and Gretchen, we need to build up our brave Tennessee members who got right back out after being forced out on a pretext, we need each and all of them. We need to stop letting Republicans control the narrative, or telling us that our candidates are old, weak, senile or unwilling to make tough decisions.
Because the recent House fight has proven that even without Trump, MAGA isn’t going away, it’s the dominant force in the party. And they’ve already proven repeatedly that they’ll crush any Democratic norms for wealth, power and ego.
