The television debate was over. The credits were rolling on the studio monitor and the candidates' microphones had been turned off. But Frank Wolf, Republican challenger for Congress who sometimes literally runs into and out of debates, could not resist one last poke.

Turning to his opponent, incumbent Rep. Joseph L. Fisher, Wolf said, "Joe, I think you should have stayed within your time limits. I stayed within mine."

Fisher, who with his gray hair and professional manner could pass for Wolf's father, replied in tones normally reserved for addressing meddlesome children: "Oh, I think I did."

In the race for Congress from Northern Virginia's 10th District, Fisher has discovered that fending off Wolf, a task that appears to make him uncomfortable, is a major part of their debates in elementary school cafeterias, confrontations in television studios or their chit-chat when hardly anybody is looking.

"He's incessant," Fisher said yesterday outside the studios of WNVT-TV (Channel 53/14) after taping an hour-long question-and-answer session aired last night."I guess he's kind of yipping at my heels all the time. He's trying to put a campaign together by attack, attack, attack."

The yipping and attacking, according to many political observers, both Republican and Democratic, is paying off.

"I wouldn't say we're worried," said Lynne Johnson, chairman of the 10th District Democratic Committee, "but I would say we are a little bit concerned."

"My gut feeling," said Nicholas Longworth, a regional political director for the Rupublican National Committee, "is that in the last six weeks of this campaign Wolf has come into his own. He may surprise a lot of people around here."

Earlier this week, at a poorly attended joint appearance by Wolf and Fisher at the cafeteria of Stenwood School on Gallows Road, Charles and Wanda Butler, two 10th District voters, were talking about Wolf.

"We met him at the Cedar Lane Safeway in the middle of the summer. He came up to us, handed me a brochure and said, 'Hi, I'm Frank Wolf.' I thought 'Who the hell is Frank Wolf?" said Charles Butler.

"And now you're hearing a lot about Wolf.I still don't know, though," said Wanda Butler.

Wolf, 39, who wears a favorite yellow-and-red striped tie and whose campaign literature notes that he "ran in the 1968 Boston Marathon and finished!" is a well-financed conservative who has been campaigning since March.

The Republican National Committee has targeted the race as one that is vulnerable and most of Wolf's $148,000 campaign war chest has come from. Republican political organizations and conservative political action committees.

But the national committee did not target Wolf as a possible winner until months ago, according to Longworth. "We made the decision based on Fisher's vulnerability, Wolf's staff and Wolf's style," Longworth said.

Wolf's tactic is to claim that Fisher's congressional voting record is to liberal for the people of the 10th District, which includes Arlington, northern Fairfax County and Loudoun County. Part of his style is to appear hunt and outraged that Fisher does not tell everybody he is too liberal for the voters.

Wolf frequently accuses Fisher of causing high taxes and also of not speaking out in favor of more federal spending for his district.

"It is hard for me to attack him," Fisher said, "because he has no record to defend." The congressman, who was a well-known economist before his election in 1974, claims that Wolf's economics are "primitive," and spending contradict his promises for budget cuts.

Several high ranking Northern Virginia Democrats interviewed yesterday said Wolf is more disconcerting as an individual than he is threatening as a congressional challenger.