Most agreed it was too hot a night to spend grilling congressional candidates, but then Democrats in Virginia's 1st District didn't really have a choice.

Their nominee for the House of Representatives had quit on them just two weeks ago and so here they were, crammed in a small, stuffy jury room in this historic town's quaint courthouse, conducting a desperate search in July for a candidate to run in the fall.

The political predicament is serious for the small group that came here from all over the sprawling Tidewater district this week. Party leaders were sheepishly pushing $10 tickets to a July 23 fundraiser--now billed as a "nomination" party. On the ticket is the drawing of a candidate's face, its features hidden by the inscription: "Watch This Space."

It's not the first time this year that Virginia Democrats have been missing a candidate. The state party spent a tumultuous spring looking for someone to run for the U.S. Senate. No sooner did the party convention in Roanoke settle that problem in early June than the congressional race in the 1st District--then considered a good prospect for a Democratic victory--blew wide open.

On June 22, Del. George W. Grayson of Williamsburg, the Democratic nominee shown by his polls to be leading against his Republican opponent, State Sen. Herbert H. Bateman of Newport News, stunned supporters by announcing he was too emotionally overwrought to continue the campaign. Since then, party leaders have been searching for a last-minute entry. So far, none of the district's best-known names has agreed to run.

As of this week, only five prospective candidates have come forward, and of those, one works for a Republican congressman and never has been involved in Virginia politics. Four were interviewed Thursday by a 12-member ad hoc screening committee in private sessions that lasted as long as an hour, a grueling experience since the candidates apparently were not offered a seat despite the oppressive heat.

Given the lateness of the hour, the panel's prepared questions--39 in all--were blunt, bypassing the usual preliminaries. "Have you ever been in trouble with the law?" went one. "How is your health?" was another. It was clear the Democrats were in no mood for more surprises.

Then there were questions with a practical bent: "What is your plan to win this election?" and "Where are your votes?" Candidates could even select their label: "Liberal--Moderate Liberal--Moderate--Moderate Conservative--Conservative." Most lined up squarely on Moderate.

Of the four interviewed Thursday, the leading contender was 1st District party chairman John McGlennon, a 32-year-old professor of government at the College of William and Mary. McGlennon is credited with keeping the Democratic campaign afloat and party spirits up after Grayson's dramatic exit.

A fifth candidate--national Democratic Committeewoman Jessie Rattley of Newport News, considered the other frontrunner for the nomination, is scheduled for an interview next week. A final decision on the party nomination will come from the Democratic District Committee in time for the July 23 announcment.

Also appearing before the committee Thursday was Lewis Puller Jr., a double amputee Vietnam veteran and the son of the late Marine Gen. Lewis (Chesty) Puller, a World War II hero. Puller ran in 1978 for the same congressional seat, losing badly to incumbent Paul S. Trible, now the Republican nominee for the U.S. Senate. John Ryland, a teacher who ran against Grayson for the nomination earlier this year and lost, also was interviewed.

The surprise appearance was by Robert Hundley, a 38-year-old Congregationalist minister who is executive assistant to Republican Rep. Thomas B. Evans of Delaware.

Hundley conceded his plans to help reelect his Republican boss this fall were a handicap and acknowledged that his political experience has been in Vermont and Delaware, and never Virginia. But he claimed other assets, including family roots in rural Essex County that go back to the 17th century. Hundley said he and Trible, also from an old Essex family, are distantly related.

But for Grayson's exit and the Democrats' sudden dilemma, Hundley acknowledged, he probably would not have sought involvement in the 1st District this year. But, he said, "being a congressman is something I always wanted to be."