While the Dems do need a deeper bench, you don’t get there by trying to primary a sitting president. It’s not going to bring anyone new to the ticket. There are several problems:

1. You’re going to lose. People who primary Biden are not running because they want to be president, because they know there is not path to victory.
2. Biden is already the compromise candidate. Fox screeching about how Biden is a communist doesn’t make him one. Republicans moving so far to the right that they’ve passed over the event horizon doesn’t make Biden a communist, either. You’re not going to get republican defectors, because just being a democrat is the bad part.
3. The only thing a primary run will do is hurt the Biden campaign in the general. You can’t win, you can’t recruit more voters to the ticket.

You aren’t deepening the bench by doing that. We had a wide array of candidates going into 2020, and we decided on a center-right safe choice for electability. You don’t deepen the bench with a failed presidential bid against your party’s incumbent.

You deepen the bench by moving people from the House to the Senate with the full support on the democratic committee, replacing people like Feinstein by pushing them out the door if necessary. You do it by advancing younger people to positions of leadership in the party and in national and state congresses. You do it by making sure people like Newsom get air time and national exposure.

I support out of state progressive candidates wherever I can, and I think we need a better organizational tool for doing so. I liked it when the Pod Saves people were trying to help identify the seats that could be flipped, and I’d like to see that extend to the state governments. We need a cohesive strategy designed to take back state governments and judgeships as well as federal offices. We will not get there by running in a primary against an incumbent president.