Sen. Bernie Sanders has raised more than $1 million for his 2020 presidential campaign in less than four hours, his team confirms, putting him well ahead of other contenders who launched their bids with strong financial support.

Sanders, I-Vermont, formally joined the presidential race Tuesday morning, telling "CBS This Morning" he intends to win the Democratic nomination and the White House next year.

"We're gonna win," he told "CBS This Morning" co-host John Dickerson. In his second run, Sanders is vowing to launch a grassroots movement that will "lay the groundwork for transforming the economic and political life of this country."

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An aide confirmed Tuesday morning that Sanders had easily raised more than $1 million in the first three and a half hours since the senator launched his campaign at 7 a.m. ET.

One senior aide who confirmed the sum added at around 7 a.m. PT, "And California is just getting up."

A full campaign finance report won't be available until later this year to independently verify the amount raised. But if true, the haul puts Sanders well ahead of other contenders who raised big money after their announcements.

In January, Sen. Kamala Harris raised about $1.5 million from more than 38,000 people in all 50 states in the first 24 hours of her campaign – an eye-popping sum that raised alarm bells at rival campaigns. The average donation was $37, her campaign said. Sen. Amy Klobuchar, D-Minn. this month also raised more than $1 million in the first 48 hours of her campaign.

Democratic Sens. Elizabeth Warren, Kirsten Gillibrand and Cory Booker did not see similar spikes when they launched their campaigns – but each has millions of dollars in their Senate campaign accounts that they can opt to transfer into a presidential campaign account. Warren had about $12.5 million in her 2018 reelection campaign coffers at the start of the year; Gillibrand had about $10 million; and Booker's campaign had about $4.1 million at the end of 2017, according to the Federal Election Commission.