Almost one-third of registered Democratic voters back former Vice President Joe Biden for the party's 2020 presidential nomination, making him the front-runner in a new poll provided exclusively to The Hill.

Biden is the clear leader in Harvard CAPS/Harris's June poll with support from 32 percent of Democrats polled. Hillary Clinton, the party's 2016 nominee, finished second with 18 percent of the vote, while her 2016 primary opponent, Sen. Bernie Sanders (I-Vt.), sits in third with 16 percent.

Sen. Elizabeth Warren (D-Mass.) was the only other candidate to poll in double digits, with 10 percent of those surveyed backing her.

Biden has spoken frankly about both his interest in running for president and his hesitancy to jump in the race.

He flirted with a bid in 2016 but ultimately decided not to run while he mourned the death of his son, Beau. This week, he joked to The Washington Post that he isn't "looking to live in the White House," but added, "I don't know what I'm going to do."

Another Clinton bid is seen as far less likely than possible bids by Sanders and Warren, who have been crisscrossing the country and heavily fundraising.

The Harvard/Harris poll also tests the 2020 chances of Sens. Cory Booker (D-N.J.), Kamala Harris (D-Calif.) and Kirsten Gillibrand (D-N.Y.), as well as billionaire Michael Bloomberg and New York Gov. Andrew Cuomo (D).

In that group, Booker fares best among respondents with 6 percent of them backing him, followed by Bloomberg's 3 percent and Harris's 2 percent. Cuomo and Gillibrand were each backed by 1 percent of those surveyed, while 12 percent said they supported someone not listed.

Unlike the 2016 field, which had been viewed as a one-person race until Sanders's surprising rise, the 2020 Democratic primary race appears to be wide open and is expected to attract more than a dozen hopefuls.