For the first time since he entered the White House, President Carter's positive rating has slipped below the 50 per cent mark. The latest Harris Survey of 1,536 adults nationwide shows that the public is split, 48 per cent positive and 48 per cent negative.

This marks the fifth month in a row that the President has dropped in his job rating. From a high mark of 69 per cent positive last April, he has slipped 21 points to his September low. While Presidents tend to lose ground after more than six months in office, these latest losses for Carter appear to be both serious and greater than normal.

In only one region, the South is Carter able to achieve better than a 50 per cent rating. There he has a 52 to 43 per cent positive standing, down from 68 to 28 per cent in July. In the East, he comes up with a 50 to 48 per cent negative rating; in the West, he is given a 56-40 per cent negative rating; in the Midwest, he receives a positive rating of 49 to 47 per cent. If the South is excluded, President Carter now has a negative rating of 51 to 46 per cent in the country.

As for other groups:

Among blacks, President Carter is able to score no better than a 49 to 45 per cent positive rating, precipitously down from the 71 to 26 per cent positive rating in July.

Among key religious groups, President Carter also appears to be in trouble. Among white Catholics, he receives a 50 to 47 per cent negative rating; among Jews, he receives 60 to 37 per cent negative marks. However, among white Protestants he still has a 50 to 47 per cent positive rating.

Among union members, also one of the key elements in the traditional Democratic coalition. Carter's job rating has fallen to 54 to 44 per cent negative.

People who classify themselves as independents have now turned negative on the President by 54 to 44 per cent.