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.

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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.

Susan Rice, the former national security adviser for President Barack Obama, caused a stir Friday afternoon when she tweeted "Me" when another former Obama official asked who could challenge Collins in 2020.

Rice does have a home in Maine, a source said, and her family has ties to the state.

In a follow-up tweet, Rice said: "Many thanks for the encourgement (sic). I'm not making any announcements. Like so many Americans, I am deeply disappointed in Senator Collins' vote for Kavanaugh. Maine and America deserve better."

Brian Fallon, a former aide to Hillary Clinton who's the head of a group that aimed to sink Kavanaugh's nomination, suggested former Planned Parenthood head Cecile Richards for the job.

"Doesnt @CecileRichards have a home in Maine?" Fallon asked. Richards does in fact own a home in the state.

Collins' speech, where she decried the process to get Kavanaugh's nomination through the Senate and slammed outside Democratic groups for their actions throughout it, so animated Democrats in Maine that many wasted no time to tout that they were openly considering a run.

"I would certainly not rule it out," Berry, who spent a decade representing rural Maine, told CNN. "There are others who are equally qualified and I would want to look at the whole field before I make a decision, but clearly Sen. Collins made a choice that did not reflect the people of Maine and our values."

Gideon also leaned into a possible run minutes after Collins' speech wrapped up, posting to her Facebook page that she will consider challenging the Republican. In an interview with CNN afterward, she called Collins' plan to back Kavanaugh "a final straw" but not the only reason.

"I am considering it," she said. "I have a very important responsibility from now until November 6 to re-elect a Democratic majority (in the Maine House), so I am laser-focused on that in the next four and a half weeks. However, this is something I am seriously considering and once we get past November 6 then I will be really laying out everything and making a decision."

Gideon added: "As a woman, it is absolutely fundamentally tied to my belief about what he will do as a justice on women's reproductive rights, but further than that, when the testimony of Dr. Ford came out, it really did become something different."

The Maine Republican Party stood firmly behind Collins after her speech, calling the remarks the "gold standard of speeches in explaining her vote and showing how a nominee should be evaluated."

But it seemed shortly after the remarks that Collins' defense of Kavanaugh invigorated Democrats in the state and nationwide.

"This will galvanize Democrats to come together and look for a strong challenger to Sen. Collins," Joe Baldacci, a former mayor of Bangor, said in an interview. "I think these votes really go to the heart of important progressive issues and how they affect Maine families, and I think this vote will galvanize Democrats in Maine."

One thing was clear after Collins' speech: Whoever runs will be well funded.

As the senator spoke, grass-roots progressive donors poured money -- more than $1 million, according to organizers -- into an online effort led by the Be A Hero PAC designed to raise money for a potential Democratic challenger. When its Crowdpac site crashed, the group set up an account on Act Blue, another fundraising website, and said it likely crossed the $3 million threshold by the time Collins finished her remarks.

Back in 2014, the last time she ran for re-election, Collins spent more than $5.5 million. Her opponent, Democrat Shenna Bellows, raised only $2.4 million.

If Collins decided to oppose Kavanaugh, the pledges would have been canceled. But the group's president, Liz Jaff, said that with Collins' announcement, "Everybody's going to get charged tomorrow."

The "Be A Hero" effort had picked up steam, and appeared in headlines, earlier in the confirmation process when Collins derided it as "bribery."

The money, which has been raised legally, is likely to change the early contours of the primary to replace her.

"Nobody ever goes in that early, nobody is even thinking about, and what we've just done is set it up for a candidate to legitimately have a chance," Jaff said. "Starting capital for any person running for Senate in Maine hasn't even been close to what we just raised. So I think what happens is suddenly you will have a bunch of people who say, 'I could never have raised that money. It's just going to be too tough,' are suddenly looking at a pool of capital they could have access to."