Sen. Eric Brakey, R-Auburn, intends to run against Sen. Angus King in the 2018 U.S. Senate race.

PORTLAND — A young Auburn legislator who began his political career on the libertarian fringe of Republican politics announced an underdog 2018 run against independent U.S. Sen. Angus King in a video given to the Bangor Daily News on Monday.

It’ll be an uphill challenge for 28-year-old Eric Brakey against King, a popular former governor. The Republican also has a potential primary hurdle in Gov. Paul LePage. Brakey would be the youngest-ever U.S. senator from Maine.

In a Saturday interview, Brakey touted his libertarian brand and stances, such as support for marijuana legalization that won him two elections in a closely divided Maine Senate district as a blueprint for statewide success. He is expected to formally announce on Tuesday.

“I am getting into this race to challenge Angus King,” Brakey said, “and I am getting into this race now because I understand that I am going to be an underdog candidate.”

Brakey, an Ohio native, began his career by tweaking Maine’s Republican establishment, but he has won key victories in the Senate, particularly as the sponsor of a 2015 law repealing the state’s concealed-handgun permit requirement.

He headed Republican Ron Paul’s 2012 presidential campaign in Maine, where Paul supporters took over the party convention to secure a majority of delegates, leading to a dispute resolved when delegates were split between Paul and Mitt Romney.

In 2014, Brakey challenged state Sen. John Cleveland, a Democrat in his fifth total term. He beat Cleveland with 59 percent of votes, won re-election in 2016 and chaired Kentucky Sen. Rand Paul’s brief presidential campaign in Maine the same year.

King has never lost: He won the Blaine House in 1994, was re-elected in a landslide, then after U.S. Sen. Olympia Snowe announced her retirement in 2012, King won her seat against weak opposition.

Brakey called King a champion of “big government and big corporations” and hit Republicans for challenging him weakly, saying his party needs a message “different from the traditional, cookie-cutter establishment” one to win. Brakey doubled down on that attack in a video announcing his campaign, using plays on King’s name to try to portray the incumbent as part of a “dynasty” committed to the status quo while presenting himself as “a leader, not a king.”

He also borrowed a variation of LePage’s successful campaign mantra, saying his focus is “people, not politics.”

LePage, who is beloved on Maine’s right, has considered challenging King since 2015. Brakey said he’s an “admirer” of LePage and that they have met to discuss the race. He demurred when asked about them, but said he didn’t think LePage “knows what he’s going to do.”

However, Brakey said while LePage could quickly assemble a campaign “because of how long he’s been in politics” and “the number of people he’s had on the political payroll,” he can’t wait.

Douglas Hodgkin, a retired political scientist at Bates College in Lewiston and a Republican, said LePage may not want to end his career by losing to King and that Brakey would likely have the energy and money to run admirably.

“Not that he’s necessarily going to win it,” Hodgkin said, “but it could be that down the line in a future year, he would have the name recognition and reputation of having run a good race despite the odds.”

Similarly, U.S. Sen. Susan Collins took third in the 1994 governor’s race that King won. The Republican won election to the Senate two years later.