Maine’s U.S. Sen. Susan Collins has raised more than $5 million for her re-election campaign, leading Democratic challenger Shenna Bellows by a wide margin.

Collins, a Republican who is seeking her fourth term in the Senate, reported $446,976 in donations during the reporting period that ended May 21. That total put Collins at slightly more than $5 million for the campaign so far. She ended the period with nearly $3.9 million remaining, according to figures from her campaign.

“We’re delighted with the overwhelming support we continue to receive for Senator Collins’ re-election,” said Betsy McCandless, treasurer for the Collins campaign, in a prepared statement. “Our cash-on-hand number puts us in a very strong position as we head into summer.”

In the same reporting period, Bellows reported surpassing $1 million in total fundraising. Bellows raised $256,581 during the most recent reporting period and had $579,864 left in her campaign account as of May 21st, her campaign staff said Friday.

Candidates for Maine’s congressional seats were required to file updated pre-primary campaign finance reports with the Federal Election Commission by Thursday night. Neither Collins nor Bellows has an opponent in their respective party primary on June 10.

In her 2008 campaign, Collins had raised $5.8 million before the June primary. She was facing a well-known and better-financed opponent, Democratic U.S. Rep. Tom Allen from Maine’s 1st District, and the campaign heated up earlier in the election cycle. The two candidates spent more than $14 million on the 2008 campaign.

Bellows is a former executive director of the American Civil Liberties Union of Maine who has been heavily involved in numerous political campaigns – including Maine’s two referendums on legalizing same-sex marriage – but is running for political office for the first time.