Herschel Shosteck ("In the Polls, a Misleading Lead," op-ed, Oct.31) was right to point out that those who participate in presidential primaries and caucuses may diverge in their opinions and behavior from the general public surveyed in the syndicated polls.

But he was wrong to conclude that this difference works to the advantage of President Carter.

His argument rests upon two propositions: 1) better-educated, upper-status persons are more apt to vote in primaries and form the constituency of President Carter, not Sen. Kennedy; and 2) caucus participants are more sensitive to the desirability of party cohesion and have a predisposition to support an incumbent president.

On the first point, there is not a shred of evidence that suggest Kennedy will fare poorly among upper-status voters. On the contrary, 1972 demonstrated the potential for disproportionate liberal strength among Democratic primary electorates. In 1976 the more liberal Morris Udall drew support consistently from professional, upper-income people while Jimmy Carter's strength came evenly from all status groups. Furthermore, poll results in 1979 reveal that better-educated, upper-status Democrats prefer Kennedy over Carter by a wide margin.

We don't know with any certainty whether the 1980 Democratic primary electorate will be unrepresentative of rank-and-file voters, as it was in 1972, or roughtly representative, as in 1976. But we do know that if any ideological bias does surface in 1980, it is most likely to have a distinctively liberal cast.

On the second point, Shosteck must be confusing today's caucuses with those of the pre-reform ear. New rules regarding timeliness, scheduling and fair reflection of presidential preference have taken the caucuses out of the hands of party regulars and into those of candidates who can generate excitement and commitment on the part of local activists. George McGovern demonstrated in 1972 that party caucuses can be dominated by persons not at all concerned with party cohesion.

A plausible argument can be made that the commanding lead in the polls Kennedy now enjoys over Carter will begin to diminish once the senator's positions on issues and his personal history receive full public scrutiny and once the onset of the campaign puts to a test whether the youngest Kennedy has rhetorical skills equal to those of his brothers. And high expectations generated in part from his commanding lead in the polls will have to be met by decisive victories in early caucuses and primaries.

A protracted and spirited contest for the Democratic nomination is a real possibility, but it is sheer fantasy to believe that Carter's present strength among those most likely to participate in the primaries and caucuses makes him the likely Democratic nominee in 1980.