The total places Kamala Harris fourth behind Democrats who have released fundraising totals.

US Senator Kamala Harris of California, who emerged as a top contender for the 2020 Democratic presidential nomination after last week's presidential debate, said her campaign raised nearly $12 million during the most recent fundraising quarter.

The total places Harris fourth behind Democrats who have released their fundraising totals: South Bend, Indiana Mayor Pete Buttigieg raised $24.8 million; former Vice President Joe Biden raked in $21.5 million, and US Senator Bernie Sanders of Vermont raised $18 million over the same period.

Harris' campaign took flight at the debate when she sparred with Biden over his past opposition to mandatory busing to integrate schools and his past work in the Senate with segregationists.

Recent opinion polls have shown her vaulting into the ranks of the top challengers to the front-running Biden, a group that also includes Sanders and US Senator Elizabeth Warren of Massachusetts. The Democratic nominee will take on Republican President Donald Trump in next year's general election.

With the fundraising quarter ending June 30, Harris' campaign had only a matter of days to turn her newfound momentum into tangible contributions.

In fact, Harris' total for the quarter almost matches her first-quarter figure, but her campaign said last week that she had raised $2 million in the first 24 hours after the debate alone, meaning that her fundraising had slowed before her exchange with Biden.

In an interview with CNN that aired on Friday, Biden admitted he had not been prepared for the aggressiveness of Harris attack.

Harris' campaign also said it had taken in close to a half-million dollars from online sales of merchandise, including T-shirts reading "That Little Girl Was Me" - a reference to Harris telling Biden that she benefited from a busing program when she was a young student.