Seattle's 7th Congressional District votes today to select party nominees for the Seat vacated by Brock Adams, one of three congressmen appointed by President Carter to Cabinet-level posts.

A record number of candidates, 24, are after the seat in the predominability blue-collar district, home of Boeing Co., Bethlehem Steel and Todd Shipyard.

Adams held the seat for 12 years, a time in which the district changed from heavily Democratic to marginally Democratic. Carter carried it by 800 votes last year.

Adams resigned to become Secretary of Transportation, starting the traffic jam that surrounds this special election. The top vote-getter in each party will advance to a May 17 general election.

The anomaly of a special election in April, one combined with a Seattle school levy vote, makes the race compartively wideopen.

Leading Democrats are lawyer Marvin Durning, state Sen. Gary Grant, and ex-state Sen. Martin Durkan, a lawyer. They are pursued by state Sen. George Fleming, state Rep. Georgette Valle and super-conservative John D. Hemenway, a former Foreign Service officer who was involunarily retired in 1969.

Republicans, who could win the seat in this offyear, have state Sen. Jack Cunningham, Norward Brooks, the former state director of employment security, and Ray Pritchard, a Boeing engineer politically blessed with the same surname as popular 1st District Republican Rep. Joel Pritchard, but little else.

Ray Pritchard, a shy man who resembles acto Don Knotts, has won the GOP nomination in the past two primaries with practically no campaign. Both times it was a trip to oblivion against Adams in the general.

Cunningham, a manufacturer, is wealthy, handsome and conservative. But some of his base of support may be taken away by two Democrats - Durkan, who has big business backing, and Hemenway, who has enthusiastic backing on the right.

Durkan has raised more than $100,000. A two-time loser in efforts to win the nomination for governor, he resigned from the state Senate three years ago and now is attempting a political comeback.

Durning's base includes liberals and environmentalists. He has an organization intact and well-honed after an unsuccessful run last fall for the nomination for governor.

Given his organization, probably best among these candidates, Durning's best hope is that a low turnout will give his followers abnormal clout.

Grant is the labor candidate. A union business agent with a nearly perfect labor voting record in his 14 years as a legislator, his contributions are as overwhelmingly from labor unions as Durkan's are from business.

Hemenway is second only to Durkan in contributions, much of it from conservatives outside the state, according to state records. A sharp critic of former Secretary of State Henry A. Kissinger, Henenway's pitch is that the United States can't be second to the Soivet Union; that national defense comes above everything else. His following includes such prominent John Birch Society members as national board Director S. J. Agnew of Centralia. Henenway is a political curiosity in that he is running as a Democrat rather as a Republican.

Issues have played little part in what has largely been an apathetic contest. Each of the candidates has promosed to improve employment, the environment and national health care. A distinction between Durkan, who has support of the American Medical Association, and Grant, Durning and Fleming rides on what kind of national health cart plan.

Durkan favors the limited "catastrophic" AMA plan. The others back full comprehensive national health care programs.

Washington state has never elected a member of a minority race to Congress. If it's to happen, it will likely be in the 7th District, where most of the state's black and Asian population is concentrated.

Democrat Fleming, a former University of Washington Rose Bowl star, and Republican Brooks both black are widely regarded as outstanding public officials.

Today's contest will likely turn on absentee ballots. About 16,000 of them are at large, many the result of organized labor's intensive efforts for Grant.

Despite the unusually high number of absentee ballots, election officials figure only a moderate voter participation - 25 to 30 per cent of the registered voters.

Washington voters are not required to register by party, so crossovers could further complicate the race.