A campaign advertisement that pictures Republican James T. Broyhill hard at work on Senate business, even though he was not sworn in as a senator until yesterday, is to be broadcast this week in North Carolina.

The ads were filmed two weeks ago, when Broyhill was a House member and the GOP nominee in this year's North Carolina Senate race. On July 3, he was appointed to fill the post held by Republican Sen. John P. East, who committed suicide June 29. East earlier announced that he was not seeking reelection.

Douglas Haynes, campaign communications director, said the ad was "scheduled and written before the tragedy happened with Sen. East . . . . Rather than say 'congressman,' as it would have before, we say 'senator.' "

The spot unreels in the fast-paced, cinema verite style that is the trademark of Broyhill's media consultant, Robert Goodman:

"Six fifty-two a.m. When most of Washington is waking up, Jim Broyhill has already been at work for 30 minutes."

A distressed elderly woman with a Social Security problem calls. He solves her case.

Then he escorts a group of schoolchildren around the Capitol. "The guys in the big limousines can wait," intones the narrator.

Next he's meeting with Senate Majority Leader Robert J. Dole (R-Kan.). "Bob Dole needs help on the tax-reform bill. Broyhill will go to work on it."

At midafternoon, he addresses a rally. "Broyhill gets his conservative colleagues behind the president's plan to cut government waste."

His wife calls. It's 5:53 p.m. "Sorry, Louise, I'll be a little late tonight. Hug the grandchildren."

Then the tag line: "And as our senator, he'll be on the first team from day one."

The fact that this day in the life of Sen. Broyhill was filmed two weeks before he became a senator has provoked caustic comment from the campaign handlers of former governor Terry Sanford, the Democratic challenger.

"You can almost hear the organ music at the East funeral playing on the sound track," said Harrison Hickman, Sanford's pollster. "One of the things Broyhill had going for him with moderate voters was that they felt he was an honorable person who would put the state ahead of his political career. He's clearly going to lose on that dimension now."

"This is instant senator," said Robert Squier, Sanford's media consultant. "You pour hot water on it and it's your senator."

Sam Poole, Sanford's campaign manager, was not sure if the ads will become an issue. "In terms of being an issue in a Senate campaign, we wouldn't make it an issue," he said. "I don't know how the voters will take it."

Another Broyhill ad, broadcast yesterday and Sunday, featured the new senator, seated before a black background, praising "our late Sen. East, a good friend," and accepting "this responsibility on behalf of the people of our state."

"This is a shocking turn of events," Goodman said of East's death and Broyhill's appointment. "Jim Broyhill simply wants to tell the people how he feels, to give them a clue about the kind of person he really is, showing a great deal of humility, tenacity and real class."