If the nuclear freeze is an issue anywhere, it is here in this enclave of pastoral affluence, where Quakers, environmentalists and liberal Republicans abide and live peacocks patrol the lush lawns.

Unemployment gnaws at the upper and lower ends of Bucks County but, in the middle, citizens who have no worries about putting bread on the table are free to consider the cosmic. Surveys show that is just what they are doing.

But the matter does not exactly hit one between the eyes in the course of a brief visit. Last Sunday, the League of Women Voters, which staged a debate betwen incumbent Republican congressman James K. Coyne and Democrat Peter H. Kostmayer, who is trying to regain the seat he lost in the Reagan sweep, did not even put the freeze question on the agenda. Afterwards, the moderator explained mysteriously, "We felt it has had enough publicity."

Paul Zimmerman, chairman of the Bucks County Alliance for Nuclear Disarmament, then told her sardonically, "No point in raising something everyone is interested in."

Kostmayer, who said he isn't sure the freeze is "the decisive factor," managed to inject a reference to it, accusing Coyne of "wanting it both ways" on the question. Coyne, who prefers not to discuss either the freeze or the fallout in the wake of his voting record on the issue, did not respond.

Offstage, he insists there is "no difference between us -- we are both for a freeze."

The thrust of Coyne's campaign is to blur all differences between him and the liberal Kostmayer. One of two fringe candidates included in the debate noted the surface resemblances between the two main contenders -- "both good-looking," he noted. They are almost of an age -- Coyne is 35 and Kostmayer 36 -- and both are fair-haired, articulate Ivy Leaguers.

But for Kostmayer, the critical difference is their positions on a halt in the arms race. He is unequivocally for the Kennedy-Hatfield resolution, which calls for an immediate bilateral freeze. Within minutes, Coyne voted for and against the House version.

Coyne was a cosponsor of the freeze resolution. On the morning of Aug. 5, he assured his constituents on a local radio station that he would be voting his and their convictions later that day. And he did, the first time around. But when the freeze was on the edge of victory, he changed his vote, coming out in favor of the "freeze later" favored by President Reagan.

"You're supposed to vote for bills you cosponsor," Kostmayer said mildly during the debate. Coyne has taken to calling the freeze he once sponsored "the Brezhnev freeze" and to labeling its advocates "irresponsible, un-American ultra-leftwingers." Kostmayer hopes that genuine doves understand the difference between "a freeze" and "the freeze." One of his commercials about the matter shows a crumbling cookie to indicate how Coyne crumbled under White House pressure.

Regarding his conversion, Coyne gives several explanations, in none of which Reagan figures. He says it was "solely my conscience" that caused the switch. He also says it was a vote-day lunch with a Harvard classmate, who warned him of the long-term consequences of an immediate freeze. He also says it was seeing on PBS' MacNeil-Lehrer Report how "partisan" the issue had become during the tense tally.

He has had some success in muddying the waters. A Bucks County voter shivering in the October winds of an outdoor Jewish rally for Kostmayer said, "They're both for a freeze, and I'm against one."

Another voter, herding children into a van at the same event, said, "The freeze is not my issue. I'm voting Kostmayer because it's a vote against Reagan -- it's the only way I can tell him what I think of the job he's doing."

Coyne says the election will not be a referendum on either the freeze or Reaganomics: "It's a referendum on two guys in this district."

In the 8th Congressional District, which has been redrawn, Republicans still have 25,000 more registered voters. To bring him home, Coyne is counting on strong Republicans at the top of the ticket, where Gov. Richard L. Thornburgh and Sen. John Heinz are expected to be easy winners.

Coyne says in one breath that there is "little difference" between him and Kostmayer, and in the next that "Kostmayer is too liberal for this district--the only Democrat they elected in 50 years." Polls have been of no help in trying to figure out if the planetary or parochial concerns will prevail. Coyne has one from Robert Teeter that shows him six points ahead. Kostmayer's, the work of Penn & Schoen, has him winning by nine points.

If it's that close, disarmer Zimmerman says, the freeze people will decide it. "They know what a real freeze is, and they'll be there," he says.