Nearly two of every three blacks in the nation disapprove of President Reagan's handling of his job, half say his economic policies have held blacks back and 56 percent say they "think of Ronald Reagan as a racist," according to a new Washington Post-ABC News poll.

The latest findings represent a decline in the black approval rating for Reagan, who, because of increased employment and a lack of controversial racial issues, received his best ratings ever among blacks throughout most of last year.

In a December Post-ABC News poll, for instance, 36 percent of the blacks interviewed approved of Reagan's handling of the presidency, while 50 percent disapproved and 14 percent offered no opinion.

A New York Times poll taken about the same time reported a 56-point black approval rating for the president.

In the latest Post poll, however, only 23 percent said they approved of Reagan's handling of the presidency, while 63 percent disapproved and 14 percent had no opinion.

The earlier polls interviewed only about 110 blacks as part of a national sample and were subject to a margin of sampling error of about 10 percentage points. The latest Post poll, however, interviewed 1,022 respondents and has a margin of error of 3 points.

"About all one can say is that 23 percent, even though it's lower than most recent polls have shown, is still better than the surveys of a year or two ago," White House political assistant Mitchell E. Daniels Jr. said yesterday. Reagan's approval rating among blacks was a rock-bottom 9 percent in an August 1983 Post poll, with 86 percent saying they disapproved.

On the view of Reagan as a racist, an accusation that particularly bothers the president, Daniels said, "He's been called a lot of unfair names over the course of time and I guess it's had some effect."

Reagan received only 11 percent of the black vote in 1984, but some Republicans have been appealing to blacks to take another look at the GOP, join its ranks and help it take the Democrats' place as the majority party.

The Post poll, however, conducted by telephone between Jan. 7 and Jan. 14, indicated that virtually every sector of black America holds the president, his party and its leaders in low regard.

Seventy-two percent of the respondents said Republican leaders generally did not care about the problems of black people, as compared to 16 percent who said they did care. The other 12 percent gave no opinion.

Three of every 10 interviewed said they thought GOP leaders were "getting better" when it came to caring about blacks, but 4 of 10 said the leaders were getting worse and 2 of 10 said they saw no change.

The poll found that, generally, the more education a respondent had the greater the likelihood of low regard for Republicans. This negative assessment was shared by blacks of all regions, ages and incomes; suburbanites, city dwellers and rural respondents; women as well as men.

When asked, "Do you think of Ronald Reagan as a racist," 56 percent -- nearly two-thirds of those who had an opinion -- said "yes," compared to 31 percent who said "no." Asked the same question about Minister Louis Farrakhan of the Nation of Islam, 36 percent -- again about two-thirds of those with an opinion -- answered "yes," and 20 percent said "no."

Many of the blacks interviewed in the latest Post poll reported far better personal economic fortunes than those interviewed in earlier surveys. Forty-one percent, nearly twice as many as in a January 1985 survey, said it was "not difficult at all" to meet monthly household expenses."

However, when asked, "Generally speaking, would you say Reagan's economic policies have helped most blacks or held them back, or made no difference one way or the other," 49 percent said "held them back," 33 percent answered "no difference" and only 11 percent said the policies had helped.

In contrast to Reagan's ratings, Jesse L. Jackson, who finished third in the 1984 race for the Democratic nomination for president, was favorably regarded by 87 percent of those interviewed. Only Martin Luther King Jr. received a higher favorable rating, a near-perfect 97 percent.

About 8 of every 10 respondents said Jackson's 1984 presidential campaign was good for blacks in the country; fewer than 1 in 10 said it was bad.

Two of three, 66 percent, said Jackson should seek the Democratic nomination again in 1988, while 26 percent said he should not. And 53 percent said it would be "a good idea" for a black leader like Jackson to run for president as an independent; 37 percent said that would not be a good idea.

Despite Jackson's continuing denunciations of the Democratic Party as disrespectful of blacks and taking their votes for granted, 71 percent of those interviewed said they thought Democratic leaders cared about the problems of blacks, compared to 19 percent who said they did not.

Exactly 50 percent of those interviewed said they thought the Democratic leaders were improving, compared to 18 percent who said they were getting worse and 22 percent who saw no change.

About 65 percent of those questioned said they usually thought of themselves as Democrats; 5 percent said Republicans. Twenty-five percent said they were independents, with a majority of them saying they leaned toward the Democrats.

Generally, the poll found that the younger the respondent, the more likely he was to consider himself an independent. However, younger respondents (18 to 30 years old) also were more likely not to be registered voters or voters in the 1984 presidential election.

Farrakhan, accused by many of being anti-Semitic but able to attract large crowds of blacks to hear his appeals for black nationalism and economic unity, was rated by only about half those interviewed. Of those, 23 percent said they had a favorable opinion of him; 25 percent, unfavorable.

Ideologically, the largest group of blacks, 27 percent, described their political views as moderate; 7 percent said "very liberal," 21 percent "liberal," 17 percent "conservative" and 5 percent "very conservative." Another 18 percent said they did not think of themselves in those terms. Polling assistant Kenneth E. John contributed to this report.