About one in 10 Biden supporters switched to Harris after the debate. That made Harris the biggest single beneficiary of Biden’s loss of support. But about twice as many people — about one in five Biden supporters — switched from Biden to a non-Harris candidate or became undecided. And as a reminder that debates usually don’t turn elections completely on their head, more than two-thirds of Biden supporters stuck with him after the debate.

Those voters who switched from Biden to Harris may not have represented a big share of Biden’s support, but they made a big difference to Harris. Almost a quarter of Harris’s post-debate supporters were Biden converts — by far her biggest single source of added support. However, she also picked up support — more than two-fifths of her post-debate support — from former backers of Warren, Buttigieg, Sanders and several other candidates. Only about a third of her post-debate support was also with her before the debate.