Norman Solomon, a Marin County political activist and author, announced Tuesday that he has raised more than $100,000 for a potential run for Congress in what is now a Marin-Sonoma district.

"We're gaining the kind of traction that a grassroots campaign needs in order to win," Solomon said. "The groundswell of support is very encouraging."

Solomon said he received donations from more than 650 people.

Assemblyman Jared Huffman, D-San Rafael, the other announced potential candidate, reported in April that he had raised more than $120,000 in donations.

Both men say they will run if Rep. Lynn Woolsey, D-Petaluma, retires at the end of her 10th term in 2012. And both have said that it could cost more than $1 million to win a wide-open congressional race.

Woolsey, 73, is expected to announce her retirement on Monday at her home in Petaluma.

Solomon, well known in the ranks of progressive Democrats, is likely to position himself as more liberal than Huffman, analysts say.

In a statement issued Tuesday, Solomon said he will advocate for "guaranteed health care, full employment, green sustainability, full funding for public education, fundamental changes in federal spending priorities and an end to perennial war."

He is now in his third consecutive term as an elected member of the California Democratic Party's state central committee.

Federal Election Commission records show that Huffman reported $123,079 in campaign donations through the period ending March 31. Solomon, who did not have a report on file, said that his first financial report is due July 15.

Woolsey reported $39,214 in donations.

Rep. Mike Thompson, D-St. Helena, the incumbent North Coast congressman and a prolific fund-raiser, reported nearly $193,000 in donations.

The North Bay political landscape appears headed for major change in 2012, as the first draft of new congressional district maps released by the California Citizens Redistricting Commission includes a coastal district running from the Golden Gate Bridge to the Oregon border, including both Huffman's and Solomon's homes but excluding Santa Rosa.

The adjacent district, which includes Thompson's home and political base in Napa County, runs inland from Santa Rosa to Yuba County, including Lake, Glenn, Colusa and Sutter counties and part of Yolo County.

Thompson has declined to discuss his plans pending final adoption of the new districts, scheduled on Aug. 15.