WASHINGTON TALK; BRIEFING

T HE seasoned bureaucrat who runs the Food and Nutrition Service is abject about the unsavory publicity that forced the Reagan Administration to withdraw its ''ketchup rule.'' Democrats are still chortling at what they hail as ''the Emperor's New Condiments'' - the attempt to declare ketchup a school-lunch vegetable.

''I let the hunger lobby groups get out in front of us on this,'' G. William Hoagland, the service director, said sadly. The opposition had a Dickensian field day of outrage and mockery that contrasted schoolchildren's shrinking meal subsidies with the Pentagon generals' groaning board of budget increases.

''I may have let the President down by not carefully orchestrating the groups,'' Mr. Hoagland apologized, vowing to go ''back to the drawing board'' for less notorious ways of meeting mandated budget cuts.

Initially, Mr. Reagan thought a bureaucrat was trying to sabotage his austerity program by making the President seem Scrooge-like in cutting milk rations to nippers. He finally decided otherwise, but David R. Gergen, the President's assistant for communications, made it clear that Mr. Reagan was still on guard.

''He's looking out for what he calls the 'Washington Monument Game,' '' Mr. Gergen said. ''The Game'' is that when cuts are proposed, for example, for the National Parks Service, resistant bureaucrats quickly announce the closing of the Washington Monument.

I N the building that houses the Constitution, archivists of the Federal Government are near the end of the enormous task of listening to all 900 of the five-inch reels of tape recordings taken from the White House of Richard M. Nixon. Listening to all these thousands of hours of talk and noise, the notorious and the mundane, the ''uh's'' and the expletives, would have taken one person 18 years. The National Archives has had nine people listening for two years, logging all of it.