(CNN) Sen. Susan Collins was already one of the Democrats' biggest Senate targets in 2020 when she took to the Senate floor Friday to announce she would vote to confirm Supreme Court nominee Brett Kavanaugh.

But Collins' decision to back the Supreme Court nominee after he was accused of sexual assault was instantly controversial with not only the hundreds of activists who flooded the Capitol this week but also with Democratic activists in her home state of Maine who have opposed Kavanaugh's nomination for weeks.

By the time she finished her speech, Democrats in Maine had begun speculating who might challenge the moderate Republican. And progressive activists are pouring in money to fund the eventual challenger, raising millions of dollars online to unseat Collins.

A half dozen Democratic operatives and lawmakers in Maine raised several names of potential candidates who are openly considering the job, including Chellie Pingree, the Democrat representing Southern Maine in the US House; Sara Gideon, the speaker of the Maine House of Representatives; Seth Berry, a former member of the Maine House of Representatives; and Hannah Pingree, a former speaker of the Maine House and Chellie Pingree's daughter. Some Maine Democrats also mentioned Jared Golden, the veteran running in Maine's 2nd Congressional District this year, as a possible challenger whether he wins or loses the race, as well as Emily Cain, a top operative at the Democratic group EMILY's List and two-time congressional candidate from Maine.

Maine's Democratic bench is not very deep, said two operatives, so the seat could also be a chance for the party to draw in a national figure or political outsider.

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