I wrote they have a plan. Here is some indication from NYT https://www.nytimes.com/live/2024/07/11/us/biden-news-trump-election

Quietly testing in polls to see what strength Harris has against Trump. She is the obvious heir. Lichtman says that his keys will withstand her appointment since she can take credit for Biden's accomplishments. She will get an outpouring of support from women of color, all women and youth. She is not tarred as badly by Gaza and Biden's fervent embrace of Netanyahu. Moslems will definitely vote for her in the hope she will bring more compassion to that issue. Watch closely. Governor of North Carolina as VP - he will bring that state with him...it's on the cusp. Trump and his minions fear her the most and are standing on their tippy toes.