Maine House Speaker Sara Gideon will soon announce her candidacy for the U.S. Senate, challenging four-term incumbent Republican Susan Collins, the Huffington Post reported Friday.

Citing five unnamed sources – three Democrats in Maine and two national Democratic strategists – the Washington, D.C.-based news organization said Gideon will launch her campaign sometime after the close of the 129th Legislature next week.

Gideon, 47, a Freeport Democrat, has flirted with the idea of a Senate run since last fall, when Collins faced enormous pressure over her vote to confirm U.S. Supreme Court nominee Brett Kavanaugh. Gideon is in her fourth and final term in the Maine House and has been speaker for the last two.

Maine Speaker of the House Sara Gideon, D-Freeport, plans to announce her candidacy for U.S. Senate, the Huffington Post is reporting. Joe Phelan/Kennebec Journal

Gideon did not respond to the Huffington Post for comment and did not immediately respond to a message left Friday with her communications director by the Portland Press Herald. She was busy Friday presiding over the House as lawmakers debated a host of bills, including the biennial budget.

Reports of a potential announcement from Gideon won’t come as a surprise within Maine’s political circles. It was widely assumed that the House speaker – regarded as a top Democratic contender in the 2020 race – would wait until after the Legislature adjourned to announce a Senate bid.

Gideon has also led the charge during the legislative session on several bedrock Democratic issues – including expanding access to abortion and offering paid family leave – that could play well with many swing female voters in Maine.

Last October, Gideon said she was seriously considering a run and was critical of Collins’ support of Kavanaugh.

Alex Stack, spokesman for the Maine Democratic Party, declined to comment on the report but said the party expects a primary.

“Senator Collins has let a lot of people down over the past two and a half years, and she’s no longer the advocate for Maine that we all thought she was – all of the polling and data shows that Mainers are ready for a change,” he said. “Now Democrats are stepping up to the plate to show what we can achieve together when Mainers, not D.C. special interests, are calling the shots.”

Collins, 66, has not said definitively that she will seek another term but already has raised almost $4 million in campaign funds and is widely expected to fight to keep her seat.

Gideon would be the most high-profile challenger yet to enter the race.

On Thursday, longtime progressive activist and State House lobbyist Betsy Sweet, who made an unsuccessful bid for the governor’s office in 2018, announced that she will run for Collins’ seat in 2020. The only other Democrat to announce is Bre Kidman, a Saco attorney, who has no elected experience.

Derek Lavasseur, a Fairfield Republican, has said he will challenge Collins in a primary and has registered as a candidate with the Federal Elections Commission, but has not reported raising any campaign contributions.

Collins last won re-election in 2014, defeating Democrat Shenna Bellows, former head of the American Civil Liberties Union of Maine and now a state senator, with more than 68 percent of the vote.

Although some polls have shown Collins losing some support, she remains popular and has unmatched name recognition.

Nationally, Democrats have been focused on defeating President Trump next year but they also have eyes on flipping the Senate. There are 34 seats in play in 2020 and Republicans hold a 53-47 advantage at present.