Washington (CNN) There's a reason, besides the pie, that cars were lined up to get into the parking lot of the American Legion hall in Kennebunkport, Maine, on a chilly night in November, and her name is Sara Gideon.

The Democratic state House speaker wants to unseat Republican Susan Collins , who has served the people of Maine as senator since 1997 and formally announced her reelection campaign in December. The event in Kennebunkport, exactly 365 days before the 2020 election, drew nearly 100 people to hear Gideon make her case.

A Democratic win in Maine is potentially key to flipping the Senate in 2020 . Gideon has already attracted backing from national Democrats. She raised more than $1 million in a week after launching her campaign and has outraised most other Democratic Senate challengers with the exception of Arizona's Mark Kelly, the astronaut husband of former Rep. Gabrielle Giffords, and Amy McGrath, who aims to unseat Senate Majority Leader Mitch McConnell in Kentucky.

Riding on growing distrust of Collins, Gideon is framing her opponent as someone who no longer represents the interests of Mainers. Over the course of her 22-year career in the Senate, Collins has built a reputation for being a moderate. She said she didn't vote for President Donald Trump in 2016, but she's disappointed those on the left since he took office when she voted for the Republican tax bill and -- most infamously in her critics' eyes -- by voting to confirm Brett Kavanaugh to the Supreme Court.

But Gideon has an uphill battle. Despite her 10 years in public service and her campaign's growing momentum, very few of her potential voters have heard her speak before, besides in her TV ads. The American Legion talk was her biggest campaign event to date, and Gideon, 47, used the opportunity to introduce herself.

The mom of three, a Rhode Island native, lives in Freeport, about an hour north of Kennebunkport. Her father is an Indian immigrant and her maternal grandparents came to the United States as toddlers, escaping the mass killings of Armenians in the Ottoman Empire . It was her husband, Ben, who was first recruited to run for the Freeport Town Council in 2009, she tells her audiences. But Gideon decided she was better suited for the job. Now, she's served nearly four terms in the state House, the last two as speaker.

"For the past four months now, in addition to those beloved and important roles in my life, every day when I wake up, I remind myself that my new job and my most important job is to challenge Susan Collins to be our next US senator," she said at the American Legion hall.

The crowd cheered. There was an energy in the room that's been building over the past three years. Trump's unexpected 2016 win and handling of the presidency since has unleashed a new determination among previously casual voters to get politically involved, to show up at town halls, to donate to campaigns out of state.

"I liked Susan Collins. I've always admired her, often times when she voted or spoke on an issue I actually agreed with her," said Donna Gaylor, a lifelong Democrat from the nearby coastal town of Wells.

"But I truly felt that she started to fence-sit on some things and waited to see where the wind was blowing, so to speak, where her party was going," she said, adding that she lost respect for the senator when she voted for the Republican tax bill and then for Kavanaugh.

"I just can't believe that she didn't understand the ramifications of that," Gaylor said.

Flipping the Senate

Democrats need a net gain of four seats to take back the Senate in 2020, or three if they win the White House. The national party has targeted Maine as a battleground state, as well as Arizona and Colorado. Money has poured in from out of state to both Collins and Gideon.

"Maine is a legitimate pickup opportunity for the Democrats. I think it's going to be Collins' toughest race to date," said Mark Brewer, a professor of political science at the University of Maine.

"But it's not the Democrats' seat to lose, beating an incumbent is very hard to do," he added.

The Maine election has all the signs of growing into an expensive and vicious race. A Burlington woman has already been found guilty of sending a threatening letter to Collins -- which she said she sent after hearing about the controversy surrounding the Kavanaugh vote. Collins was a target of protesters at the time, who participated in sit-ins in her office.

Gideon is refusing to take corporate PAC money and calls for getting corporate donations out of politics. She often points out that Collins has taken more than $1 million from drug and insurance corporate PACs during this election cycle.

"A lot of what is preventing us from getting things done on the federal level is that there is too much influence form special interests over members of Congress," she told CNN earlier in the day.

But Republicans scoff at Gideon's criticism of Collins for taking corporate money, arguing it's hypocritical because she took money from companies while serving in the state senate, and isn't shunning money from party leadership PACs now -- which could be funded with corporate PAC money.

"Sara Gideon's claims about corporate PAC money are a joke. She built her entire political career accepting corporate money through her leadership PAC," said Jason Savage, executive director of Maine Republican Party.

Gideon is also taking heat for an ethics violation. Last month, she was fined $500 by the Maine Ethics Commission over donations made in her name in 2015 and 2016 to her now dissolved leadership PAC. The contributions are also subject to complaints filed with the Federal Elections Commission. The complaint was filed by a former Republican member of the state senate.

"It should come as no surprise that Speaker Sara Gideon was unanimously found guilty by the Maine Ethics Commission today for being a straw-donor for her corporate-funded PAC. Her clear and blatant violation of the law was clear and we are glad to see she is being held accountable," said Maine GOP Chairwoman Demi Kouzounas in a statement.

But Gideon has said that it was a mistake and she was "given incorrect guidance" on how she could make the contributions.

Her campaign points out that that the commissioners "saw no intention by Speaker Gideon to mislead or deceive" and declined to investigate the matter.

"There are people that are trying to make that into something that it's not," she said when asked about the fine by a constituent at the American Legion Hall event.

Maine's moderates

Maine has a long history of electing moderates. The late Sen. Margaret Chase Smith and former Sen. Olympia Snowe both earned reputations as moderate Republicans. Maine's other sitting senator, Angus King, is an independent who caucuses with Democrats.

Collins has been consistently ranked the "most bipartisan" senator, based on the degree she works across party lines.

"To suggest Senator Collins has changed is laughable. She is constantly being criticized by extremists on the far left and the far right, yet she has never wavered," said Kevin Kelley, a spokesman for Collins.

"Republicans, Democrats, and Independents are yearning for pragmatic, common sense leadership, and that's what Senator Collins has always, and will continue to, bring to the table," he added.

Maine voted for Barack Obama twice and split its electoral votes between Trump and Hillary Clinton in 2016. But Collins supporters point out that Collins won big even during those years. Voters also replaced Republican Governor Paul LePage, an ardent Trump supporter, with Democrat Janet Mills last year.

"I don't think she's changed a bit," said Ben Gilman, who has worked Maine campaigns for the Republican party for 25 years and currently serves as general counsel to the Maine Chamber of Commerce.

Collins also carries some weight with voters because she was born and raised in Maine herself.

"It's a big rural state and Sen. Collins has probably been to every town. She's been the bean suppers and the opening days to hunting season. They know her," Gilman added.

Gideon is also positioning herself as someone who can reach across the aisle and often talks about her record for getting things done in a divided government.

"There is one thing I want you to know about me and that is that I know how to stand up to a bully. But maybe more importantly than standing up to a bully, I know how to work around somebody like that," she said at the American Legion Hall.

During her first term as speaker of the state House, LePage was governor and the Senate was also under GOP control. But Gideon was able to build bipartisan support for a bill that expanded access to the overdose-reversing drug naloxone -- enough to even override LePage's veto.

"Sara marshaled the votes," said Chris Babbidge, a Democratic state Representative who introduced Gideon at the Monday night event.

She's also had to build support from her colleagues in the House to be chosen as Assistant Majority Leader and then as Speaker for two terms.

Gideon was selected by her colleagues as House Speaker after just two terms as a representative. "It demonstrates, I think, some remarkable skills," said Jon Hinck, a former Democratic state House representative who also challenged Snowe for her Senate seat in 2012 but lost in the primary.

Health care is top of mind

Gideon smiled warmly when she walked into the Portland Public Library for a roundtable discussion her campaign organized on prescription drug prices last week. She circled around, greeting each of the seven constituents with a handshake, asking where they live and what brought them out on a Monday morning.

For Maine, one of the oldest states in the country, affordable drugs and health care are top of mind for many residents, and Gideon has made it her primary campaign issue. She's held similar listening sessions across the state. It's mostly senior citizens that showed up in Portland. One of them was wearing socks with Michelle Obama's face on them. She and another woman said they participated in a sit-in at Collins' office, protesting her vote on Kavanaugh.

"Thank you for doing that," Gideon said.

Gideon is a natural in this environment. She asked each person to share their experience and easily guides a thoughtful discussion on what at times becomes a rather wonky topics -- ranging from importing pharmaceutical drugs from Canada (something Maine has asked the federal government for permission to do) to capping out of pocket costs for Medicare recipients to " Medicare for All " (she has some concerns and wants people to be able to keep their private insurance).

All the while, she was weaving in what the state legislature has accomplished under her term and arguing that Collins has jeopardized the Affordable Care Act by voting in favor of doing away with the penalty for not having insurance, otherwise known as the individual mandate, as part of the Republican tax bill.

Collins is a rare GOP defender of the Affordable Care Act and had previously cast a critical vote against Republican efforts to repeal the health care law.

Gideon took notes throughout the hour-long meeting, tells one man that her staff will follow up to help with a billing issue, and wrote down the name of a prescription drug coupon service for another. It was clear she's spent time knocking on doors and listening to constituents' stories on a very local level.

"In some ways it's been the most challenging work I've done because you're talking about people's house, their backyard, their children their schools -- the things that are the most emotional," she said afterward.

Out of state attention

There's money waiting for whoever wins the Democratic primary. Progressive advocacy groups that organized many of the protests around the Kavanaugh vote have raised $4 million for Collins' challenger.

But there are still seven months until the primary and Gideon has to run against at least two other Democrats: Bre Kidman, an attorney and activist, and Betsy Sweet, a longtime advocate for women's rights in Maine who ran in the Democratic primary for governor in 2018.

Kidman has raised about $14,000 and Sweet has raised $183,000. Both have criticized the national party for hand-picking Gideon and telling Mainers who their candidate should be.

"The playbook out of Washington on the way to win this race, is to raise a ton of money from wherever you can get it and run negative ads. To me, that's a stale playbook and it's not going to beat Susan Collins," said Sweet, who's held 19 town halls to date and is focusing on building grassroots support.

Still, it will be hard to contend with the war chest Gideon has amassed.

"When you have a lot of money, you're reported on like the only candidate that matters," said Kidman, who was the first to jump in the race.

"When we say the person with the most money in the race is the best person in the race, I think we're undermining the legitimacy of our democracy," she added.

CORRECTION: The story has been updated to accurately reflect Gideon's record as elected speaker.