The two opponents -- Montgomery County Executive Sidney Kramer and challenger Neal Potter -- showed up the other night to tape a cable television news program.

But the real show apparently began before the cameras started to roll.

In a burst of anger uncharacteristic in Montgomery's staid politics, Kramer, 65, turned to his 75-year-old challenger and snapped, "I will kick your duff," according to Potter.

However, workers at the Rockville cable station who overheard the encounter as the two men waited Thursday night to go on the air recalled that the word "butt" was used.

Asked yesterday if that version was true, Potter shrugged, "It's the same thing, the same degree of obscenity."

Despite the fact that two others overheard the remark, Kramer emphatically denied that he made the statement or that he engaged in a heated discussion.

"He is hallucinating," Kramer said of Potter.

Kramer characterized the exchange as a "moderate conversation between two opponents."

Kramer is seen as a favorite in his bid for a second term over Potter, a five-term council member who launched his surprise campaign for executive at the last possible moment a month ago.

Thursday's incident was a surprising outburst that quickly yesterday became the talk of county political circles.

Kramer has a stiff public demeanor -- keeping a close guard on his emotions. Potter is soft-spoken and gentlemanly in an almost old-fashioned manner. Each man has spoken fondly of the other, with Potter even saying he considered Kramer a friend.

Kramer recently sent a letter to Potter asking him to reject any "name-calling or innuendo" in the campaign and, in an unusual request, suggested that each candidate clear controversial charges with the opposing campaign before publicizing them.

Potter promised he would not run a negative campaign and would stick to the issues, but rejected Kramer's request to clear campaign statements.

Potter is critical of Kramer's policies, which he says have led to overdevelopment and high taxes. Kramer counters that any overdevelopment is the result of past council decisions, of which Potter was a part, and that his administration has worked to slow growth in the county.

The Thursday night incident occurred as the two men sat in a small conference room at Montgomery Community Television Inc. waiting to tape a "News Counterpoint" program.

The men were alone and the door was open.

Potter said Kramer said this to him: "Look. You and Dave Scull . . . . I kicked his duff last time and I will kick your duff this time."

Scull is the former county council member who ran against Kramer in 1986, losing in the Democratic primary by a nearly 2 to 1 ratio.

"I heard 'I am going to kick your butt,' " said Bill Randolph, a director of Metropolitan Community Productions Inc., which produces "News Counterpoint."

The other witness, who agreed to be interviewed only on condition of anonymity, said, "The only thing I can swear to is one phrase: Kramer was yelling 'I am going to kick your butt.' Other things were said; harsh things, but I can't tell you what the words were," the other witness said.

"It was astonishing," Potter said.

"He was clearly, deeply furious that I had entered the race."