As he approaches his 100th day in office, President Reagan. largely by virtue of his charisma appears to have overwhelming public support for his propposed cuts in taxes and in spending on social programs despite a belief by large segments of the population that both proposals are unfair.

The public opposition that began to emerge in March, before Reagan was shot in an assassination attempt, appears to have been blunted, at least for the time being, by a burst of admiration for the president's courage and good humor after he was wounded on March 30.

There are signs of dissatisfaction with Reagan's handling of foreign policy. The majority of black Americans still seem to view Reagan with distrust, and the president's early actions on the energy problem and unemployment are drawing mixed reactions from the electorate.

But, overall, Reagan's magnetism is currently so strong that the majority of Americans express a willingness to follow wherever he chooses to take them.

These are among the chief findings of a national Washington Post-ABC News public opinion poll conducted this week. Reagan, who was elected largely because of discontent with the presidency of Jimmy Carter, has now achieved immense personal popularity in his own right.

"I like the way he can take something serious and make it not so serious," said one Minnesota 18-year-old, "like the way he did when he got shot. He didn't panic or anything."

A 35-year-old Louisiana woman, an independent who voted for John B. Anderson for president last year, remarked: "What I like most about him is that when he was shot, he showed good humor and compassion for those who were shot with him."

In personal measure, Reagan stands about as high as anyone who espouses such controversial programs could. Nearly three out of four of those polled -- 73 percent, to be exact -- say they approve of his handling of the presidency. When asked to describe their feelings toward Reagan and nine other prominent national figures, citizens assign far higher ratings to Reagan than anyone else.

And asked how they would vote today if Reagan were running in a new election against Carter, Sen. Edward M. Kennedy or former vice president Walter F. Mondale, the public chooses Reagan by ratios of 2 to 1 or higher in all three instances.

Typical of this striking public admiration for Reagan is the response from an upstate New York woman, a 32-year-old Democrat who voted for Carter and who says she would vote for Carter again today if the 1980 elections were higher today.

By and large, she takes a dim view of Reagan's proposals, saying that his planned spending and tax cuts will not help end inflation. She said she believes that the spending cuts will hurt the poor, the tax cuts will benefit the rich and that Reagan's stance toward the Soviet Union is increasing the chances of war.

Nevertheless, she supports the spending and tax cuts that Reagan wants. When asked to describe in a few words what she most likes or dislikes about Reagan, she said:

"Well, he's a colorful person. He's trying to give our country a high integrity symbol with spit and polish, and he's shaking the roots . . . He's doing something, he's moving. I'm a Democrat, but my president is my president. He shows a lot of courage, he's got guts."

In terms of Reagan's policies, the Post-ABC poll found that the most widespread concern centers on his handling of relations with the Soviet Union. Forty-one percent of those polled see the Soviet Union as militarily stronger than the United States today, while 18 percent feel the United States in stronger and 36 percent see the two superpowers as about equal im might.

Reagan has maintained that the United States should strengthen its military power so that it has a "marign of safety" over the Soviets. But the public, by 65 to 31 percent, rejects the concept in favor of a potential "agreement that would leave both countries as equal as possible in military strength."

While 39 percent of those polls say Reagan's approach to the Soviet Union is reducing the chances of war, 34 percent express fear that his hardline approach is increasing the likelihood of war between the two nations. But only 12 percent of those interviewed say that Reagan is not handling relations with the Soviets as well as Carter did.

In domestic matters, Reagan, like Carter before him, draws higher grades for his personal attitudes then for his political ideas or achievements. g

The Post-ABC News poll asked people to rate Reagan from zero to 10 on his integrity, his leadership qualities, his intelligence, his handling of the energy problem, his handling of the economy, his handling of relations with Congress and his handling of environmental issues.

On each of the questions dealing with personal attributes, Reagan drew rave notices. He was rated 7.7 overall on integrity, 7.6 on leadership qualities, 8.0 on intelligence.

In the policy areas, he scored higest on his dealings with Congress, with an average rating of 7.0. His worst score, a 5.7, came on his handling of the energy problem, and his second worst, a 5.8 came on his handling of environmental issues. He drew a 6.3 for his handling of foreign policy and a 6.5 for his handling of the economy.

By contrast, when a similar set of questions was asked about Carter in a Washington Post poll in May 1979, Carter's highest rating was a 5.9, for his integrity. In that poll, Carter drew a 3.8 for his handling of the economy another 3.8 for his handling of the energy problem, and a 4.9 for his leadership qualities.

In the Post-ABC News poll, the 1,515 people interviewed were asked whether Reagan's proposed cuts in government spending would affect all segments of the population equally or whether the poor or some other group would be hurt disproportionately by the cuts. Then people were asked whether they approved or disapproved of the spending cuts, regardless of what group or groups might be hurt.

Only 24 percent said they feel that all people would be hurt equally by the spending cuts. Among them, the cuts are favored by an overwhelming 78 to 20 percent. But among the rest of the population, most of whom feel that the cuts fall most heavily on the poor, there is still strong majority support. They favor Reagan's spending cuts by a 57 to 36 proportion.

In answer to another question, one-third of those interviewed say that Reagan is "going too far in his plan to eliminate government social programs"; 42 percent say his proposed cuts "are just right," and 18 percent say Reagan "is not going far enough in cutting back or eliminating social programs.

Reagan's proposed 30 percent, three-year reduction in federal income tax elicits a similar response. Two out of three among those polled say that one group of Americans more than another will benefit most from the tax cuts, with just about half saying that it is the rich who will gain the most. Only 27 percent feel that all Americans will benefit equally by reduced taxes.

Nevertheless, there is overwhelming support for the program. Those who think all will benefit equally favor it by 83 to 14 percent; those who think one group will benefit more than others approve of it by 62 to 31 percent.

Critics of Reagan among those interviewed tend to focus of what they consider a callousmess toward the poor. "He's very outgoing and he's a people person," said a 42-year-old Connecticut woman when asked what she most likes about the president. Asked what she doesn't like, however, she said: "He doesn't have the sensitivity towards the poor people." How the Survey Was Conducted

The Washington Post-ABC News poll of attitudes toward President Reagan's first 100 days in office was conducted Monday through Wednesday, with a random sample of 1,515 adults interviewed by telephone nationwide.

Theoretically, figures based on a sample that size are subject to a sampling error of less than 3 percent in either direction, 95 percent of the time. Figures based on smaller groups within the sample are subject to a slightly higher margin of error.

The latest available U.S. Census figures on age, sex, education and race were used to adjust the sample slightly so that it matches the overall U.S. population in those characteristics.