In two potentially key political races next year – for a U.S. House and a U.S. Senate seat – the incumbents have yet to see signs of a serious challenge.

Though Maine’s 2nd District congressional race is on both parties’ list of swing districts, three-term U.S. Rep. Jared Golden, a Lewiston Democrat, is running far ahead of any potential contender when it comes to fundraising.

Golden has so far raised $862,000 for his race in the sprawling, Republican-leaning district while the sole GOP candidate, Robert Cross of Dedham, has collected $37,000, according to records at the Federal Election Commission.

If the race proves as tight as previous ones in the district, both parties will spend millions on it. Independent political action committees will likely pour in millions more.

In the U.S. Senate race, which so far has no Republican contenders, two-term independent Angus King has $808,000 of cash in his campaign coffers.

The only other candidate who has filed with the Federal Election Commission is Democrat David Costello of Brunswick. He has $32,000 in his campaign treasury after raising $36,000 since entering the race, including $20,000 that Costello loaned to his campaign.

The last time King ran, in 2018, he raised $5.5 million to win a three-way race against Republican Eric Brakey and Democrat Zak Ringelstein. The two challengers pulled in $1.3 million between them and finished well behind King on Election Day.

In Maine’s 1st District, longtime U.S. Rep. Chellie Pingree, a Democrat, has $398,000 on hand for her campaign. A Republican hopeful, Andrew Piantidosi of Cape Elizabeth, raised $21,000 by the June 30 filing deadline.

Pingree represents a heavily Democratic district where her challengers have never come close to threatening her hold on the seat she won in 2008.

Other candidates are expected to jump into the races in the coming weeks and months, but it’s not yet clear which potential challengers will decide it’s worth taking on incumbents who have shown their political savvy against tough foes in previous elections.

Members of the U.S. House serve two-year terms. Senators serve six-year terms.

The House and Senate races will be ranked-choice elections, as will any primaries that might be required for either party to pick a nominee.