President Biden’s performance at last night’s CNN Presidential Debate has left the Democratic Party confronting the possibility of replacing their presidential nominee.
This guide explains how such an extraordinary move could occur.
Biden is currently the presumptive Democratic nominee, because he has secured the overwhelming majority of pledged Democratic delegates awarded after each state's primary election.
Former President Donald Trump is also currently a presumptive nominee.
Democratic National Committee rules give the power of the nomination to those delegates.
Delegates must "in all good conscience reflect the sentiments of those who elected them," meaning Democratic primary voters.
In other words, as long as Biden wants to stay on the ballot, then those delegates are expected to vote for him.
Since the rules do not impose any legal obligation on delegates to vote for the candidate to whom they are pledged, a mass defection is at least theoretically possible.
The party will formally nominate Biden when the delegates participate in a roll call vote.
That normally takes place during a party convention, which for Democrats begins on the week of Aug. 19.
But this year, the Democrats have said they will hold a "virtual" roll call vote by August 7 to comply with an Ohio ballot access deadline.
Following legislation signed by Ohio Gov. Mike DeWine that moves the deadline to Sept. 1, Democrats no longer need to hold this virtual vote ahead of the convention.
But for now, the plan is that a willing Biden will become the nominee on August 7 at the latest.
If Biden steps aside before the roll call, then his delegates will no longer be pledged to him, and it will be essentially "open season."
Any candidate who is eligible to be president could emerge, including candidates who did not run in the presidential primaries, and delegates could vote for them.
Clearly, an endorsement from Biden would be critical for any one of those candidates.
And while the most logical contender to receive an endorsement would be Vice President Kamala Harris, Biden could choose anyone.
Any change in the nominee after the roll call vote would be even more of a political disaster.
DNC rules give broad power to the committee to replace a candidate in the event of death, resignation or "disability" of a nominee: "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."
The scope of "disability" will be a subject of intense debate if the party chooses to invoke that provision.
But in the event of one of those three conditions, the party's chair Jaime Harrison would consult with Democratic leaders. He would give a recommendation to the DNC. The committee would decide a new nominee.
Again, the most likely contender would be Harris, given her current position within the Biden administration, but anything could happen.
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If one of these conditions occurs after general election ballots are printed – and/or it is too late to change the name of the candidate printed on those ballots – the mechanism for the DNC to replace Biden is the same.
Under that scenario, the party would have to inform voters that even though they are voting for Joe Biden, the committee has chosen somebody else for the nomination.
After the election, the party would have to try to instruct electors in the Electoral College to cast a ballot for that new candidate.
The confusion that a last-minute move like this would cause among voters would make an already challenging campaign even more of an upward climb.
And given the unprecedented nature of such a move, it would almost certainly be litigated at the U.S. Supreme Court.