Where Kamala Harris’s new voters came from

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.