She’s not running for president — yet — but Hillary Clinton was the top choice for Democratic voters in the Harvard-Harris national poll released last week.

Mrs. Clinton drew 21%, followed by former Vice President Joseph R. Biden with 20%, when registered Democrats were asked whom they would support for the 2020 party presidential nod if she and former Secretary of State John Kerry were added to the mix.

Placing third in the hypothetical race was Vermont Sen. Bernard Sanders at 12%, followed by Massachusetts Sen. Elizabeth Warren at 9% and ex-New York City Mayor Michael Bloomberg at 7%.

The online survey of 1,859 voters was conducted Nov. 27-29, a few days after Mr. Bloomberg entered the race, by the Harris Poll, and released by the Center for American Political Studies at Harvard.

In the current primary field without Mrs. Clinton, Mr. Biden led the pack with 29%, followed by Mr. Sanders with 16%, Ms. Warren with 13% and Indiana Mayor Pete Buttigieg with 8%. Both Mr. Bloomberg and Mr. Kerry drew 5%.

The 2016 Democratic presidential candidate, Mrs. Clinton told BBC last month that she had no plans to enter the 2020 contest, although she added, “I never say never to anything.”