Former Vice President Joe Biden, who is mulling a White House bid, leads declared and potential Democratic presidential candidates in support among millennial voters, according to a new poll of adults between the ages of 18 and 34.

The poll, organized by the University of Chicago's GenForward Survey Project, found that 21 percent of millennials back Biden over Democrats who have entered the crowded primary field, including Sens. Bernie Sanders, Kamala Harris, Cory Booker, Amy Klobuchar and Elizabeth Warren. Sanders, whose insurgent 2016 campaign was fueled by ardent support among young progressive voters, is a close second at 18 percent.

According to the poll, Biden also enjoys strong support among young minority voters. With support from 29 percent of Asian American millennials, 28 percent of African American millennials and 19 percent of millennial whites, the former Delaware senator led in all surveyed voting blocs — except millennial Latinos. Twenty-six percent of Hispanics between the ages of 18 and 34 said they support Sanders. Among that group, Biden came in second with 19 percent support.

For months, many Democratic operatives, donors and voters have been encouraging Biden, who served as vice president for eight years under President Obama, to launch a presidential campaign and challenge President Trump in 2020. He was cheered during an event in Delaware on Saturday when he said he had the "most progressive record of anybody running." Biden later corrected himself, saying that he meant "anybody who would run."

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If he launches a campaign, Biden is likely to quickly solidify himself as one of the most formidable Democratic contenders. Unlike most of his would-be competitors, Biden is already a household name, and his allies argue he has the best chance to woo voters in states like Michigan, Wisconsin and Pennsylvania who propelled Mr. Trump to victory during the 2016 election.

The former vice president, however, will also face scrutiny from progressives for some of the positions he held during his decades in Congress.

As a senator, Biden opposed busing to desegregate public schools in the 1970s and oversaw the contentious Anita Hill hearings during the confirmation process for then-Supreme Court nominee Clarence Thomas in 1991. He also helped lead efforts to pass the Violent Crime Control and Law Enforcement Act of 1994, which many believe fueled a period of mass incarceration that disproportionately affected African Americans and other minority groups.

Biden has since embraced more progressive policy stances. This would be Biden's third presidential campaign, having run for and lost the Democratic nomination in 1988 and 2008.

The nationwide poll was conducted among 2,134 millennials between February 8 and February 25. The margin of error for the poll is 3.5 percentage points.