The November ballot will pit a fundraiser for a powerful Sacramento interest group against a political newcomer borne from the Tea Party in the Democratic 53rd Assembly District.
Betsy Butler beat out seven opponents to win the Democratic nod in Tuesday's primary, securing 26.7 percent of the vote with all precincts reporting.
Butler, who worked in the political arm of the Consumer Attorneys of California, which represents trial lawyers, was targeted with a more than $600,000 attack campaign from independent expenditures funded by insurance companies and other business interests.
James Lau, director of the California League of Conservation Voters Education Fund, trailed with 17.8 percent of the vote. He had been supported by independent expenditures from medical malpractice insurance and doctors' groups.
Butler will face Republican Nathan Mintz,a 26-year-old political newcomer active in the local Tea Party, and Green Party candidate Lisa Ann Green November in the race to replace termed-out Assemblyman Ted Lieu, D-Torrance. Mintz, an engineer, and Green ran unopposed in their primaries.