Joe Biden deciding to run for a 2nd term at the end of which he would be 86 years old.
This resulted in the unmitigated DISASTER of the "debate" with Trump; months of turmoil about whether Joe would drop out of the race; then a shortened campaign for a replacement nominee who was NOT at the top of the ticket in the primary election.
All things considered, I thought Harris did a good job and the convention was very well orchestrated, but the damage could not be overcome.
We needed the Democratic nominee to emerge from an open primary showcasing the next generation of Democratic leaders proving their mettle.
A strong articulate leader who could effectively smack down Trump and his incessant lies on the debate stage and throughout the campaign.
Who could clearly and boldly articulate a vision for the future in which the American people would be better served by their government with Democrats in charge.
Who actually won the votes of Democrats in an open primary and generate enthusiasm in the general election, motivating souls to the polls.