Vermont Sen. Bernie Sanders raised more than $1 million within hours of launching his 2020 presidential bid.

That's according to a person familiar with the campaign who wasn't authorized to publicly disclose the early numbers and spoke to The Associated Press on the condition of anonymity. The numbers were amassed less than four hours after Sanders announced Tuesday morning that he would run again.

Sanders identifies as a democratic socialist and unsuccessfully challenged Hillary Clinton during the 2016 Democratic primary.

Few candidates seeking the 2020 Democratic nomination have voluntarily released early fundraising figures.

California Sen. Kamala (KAH'-mah-lah) Harris reported raising $1.5 million in the 24 hours after she launched her campaign last month. Minnesota Sen. Amy Klobuchar (KLOH'-buh-shar) reported raising $1 million in the 48 hours after launching her campaign this month.