In Times/Siena polls of Maine, North Carolina and Arizona released Friday, voters preferred Mr. Biden to select the next Supreme Court justice by 12 percentage points, 53 percent to 41 percent. In each of the three states, Mr. Biden led by just a slightly wider margin on choosing the next justice than he did over all.

Similarly, a Fox News poll last week found that voters nationwide trusted Mr. Biden over Mr. Trump — by seven points — to nominate the next Supreme Court justice. Here again, Mr. Biden led by a slightly wider margin on this issue than he led Mr. Trump.

Among issues favorable or unfavorable to the two candidates, appointing a Supreme Court justice ranked somewhere in the middle of those tested by the survey. It was a better issue for Mr. Trump than handling of the coronavirus or race relations, but a much better issue for Mr. Biden than the economy or law and order.