Story highlights The fundraising and travel comes after a quick star turn for the freshman senator, who took office in January

Aggressively challenging Trump nominees and administration officials is advantageous for Harris

Washington (CNN) Sen. Kamala Harris is using her newfound progressive stardom to raise money for her Democratic colleagues -- and amplifying buzz about the California freshman as a prospect for the party's 2020 presidential nomination in the process.

In the first six months of 2017, Harris has raised more than $600,000 for a dozen Senate colleagues -- including $365,000 from small-dollar online contributions, her aides said.

The email list Harris has used to raise the bulk of that money is 10 times the size it was at this time last year, during her Senate campaign. She's used that list to raise money for incumbents up for re-election in the 2018 cycle, including Missouri Sen. Claire McCaskill, Montana Sen. Jon Tester and Massachusetts Sen. Elizabeth Warren.

Harris is also planning a travel schedule in the fall to raise money for Democratic Senate incumbents as well as the challengers for seven Republican-held House seats in California that the party is targeting.

The fundraising and travel comes after a quick star turn for the freshman senator, who just took office in January.

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