They would be permitted to replace him up to their convention which is very late, but if they waited that long it would mean less time to mount a campaign. After the convention they would have a lot of difficulty replacing him with anyone other than Harris. One thing the GOP could do to make it hard on the Dems would be to nominate Tim Scott for VP. That would make it very difficult for the Dems to replace Biden with anyone other than Harris. And Harris would be suicide.
It's just too late and too problematic.
What they can do is replace Kamala Harris with a new VP,- soon to be President (wink , wink) who would be more popular with Democrats.
Hillary or the Mooch would be the logical replacements with the Mooch being the front runner. Obama is already running Joe so why not make it official
Here are the current DNC Convention rules: https://democrats.org/wp-content/uploads/2023/03/2024-Call-for-Convention.pdf
IX. Procedural Rules of the 2024 Democratic National Convention
G. Filling a Vacancy on the National Ticket: In the event of death, resignation or disability of a nominee of the Party for President or Vice President after the adjournment of the National Convention, the National Chairperson of the Democratic National Committee shall confer with the Democratic leadership of the United States Congress and the Democratic Governors Association and shall report to the Democratic National Committee, which is authorized to fill the vacancy or vacancies.
Per wiki, In 2021, Jaime Harrison was selected by President Joe Biden to Chair the Democratic National Committee, and his nomination was approved by its members.
The Current Leadership is:
Chair: Jaime Harrison, former Chairman of the South Carolina Democratic Party
Executive Director: Sam Cornale, former Chief of Staff of the Democratic National Committee
Deputy Executive Director: Roger Lau, former Campaign Manager for Elizabeth Warren for President
Political Director: Alana Mounce, former Executive Director of the Nevada State Democratic Party
Chief of Staff: Anatole Jenkins, former National Organizing Director for Kamala Harris For The People
Vice Chair of Civic Engagement and Voter Participation: Keisha Lance Bottoms
Vice Chairs:
Gretchen Whitmer, Governor of Michigan
Tammy Duckworth, U.S. Senator from Illinois
Ken Martin, Chair of the Minnesota Democratic-Farmer-Labor Party
Treasurer: Virginia McGregor
Secretary: Jason Rae
Finance Chair: Chris Korge
In addition, a National Advisory Board exists for purposes of fundraising and advising the executive. The present chair is Elizabeth Frawley Bagley, former U.S. Ambassador to Portugal.
If Biden is replaced it’s a tacit admission by the democrats that they have conceded the White House are battling to save the down ballot from massacre.
For someone to step in at the last second and win would require a superstar, and not just a superstar but a superstar’s superstar and the democrats don’t have anyone like that on their bench, no one. If they did they would have run them in the first place and never let the potato run at all.
They can pic someone who may motivate their base to turn out better than the Potato, but they can’t win the White House with that, they can only win if they can solidify and motivate the base and win the independents and no one they can stick in at the last moment can do that and they know it.
So replacing the Potato is about stopping the down ballot hemorrhaging by at least solidifying the base to make sure that low advantage blue districts for elected Republican congressmen because Potato can’t motivate the base to show up.
If Potato is replaced, especially after the convention, the Dems are openly conceding they have lost the WH are are simply tryin for stem the bleeding as much as possible down ballot