Public concern about inflation has risen dramatically in the past few months and is becoming an increasing factor in the presidential campaign, according to the findings of a nationwide Washington Post poll.

Strikingly, this concern does not seem to be helping the candidacy of Edward M. Kennedy, despite the fact that the Massachusetts senator is the presidential contender who has hammered away at inflation the most.

In stead, what may be described as a near-panic mood appears to be working in favor of Ronald Reagan, a candidate who has complained bitterly about the workings of big government but who has, to date, had comparatively little to say about inflation.

Almost half the 1,873 people interviewed by The Post in April expressed the fear that they will be worse off financially next year than they are now -- a rate double that found as recently as last November.

In the new Post poll, almost 700 of the people who were interviewed in November were reinterviewed. Among those who felt in November that their financial outlook for the year ahead was bright, more than half have changed their minds and now feel they will be worse off financially in the days ahead.

All across the country, people reported cutting down on gasoline consumption, taking on extra jobs, borrowing to make ends meet and looking for ways to cut spending even further.

"We're farmers and we have tremendous expenses," said Jack Merrick of Causey, N.M. "Of all the things that are essential, we're trying to figure out just what can be cut, and it's tough."

Merrick, who calls himself a political independent, said he would vote for Reagan over Kennedy if the two won their parties' nominations, and that he leans to Reagan over President Carter if the president is renominated.

Merrick is one of a great many who seems to be thinking that way: Reagan, maybe; Kennedy, no.

The Post's poll was conducted from April 9 through April 13, during the three-week lull in the presidential primary season. Because it was conducted nationally, it has no bearing on what may happen in tomorrow's Pennsylvania primary. Voters in any one state may have views far out of line with such a sampling of national opinion.

Nationally, the 757 people who identified themselves as Democrats in The Post's poll chose Carter over Kennedy by almost 2 to 1 -- 59 percent to 30 percent. Among registered Democrats, Carter's majority was slightly higher, and among Democrats and people who called themselves independents it approached 2 1/2 to 1.

A cross-tabulation of the poll shows how politically ineffective inflation has been as an issue for Kennedy. Among Democrats and independents who feel they can keep ahead of inflation and will be better off next year than they are now, Carter is preferred over Kennedy by 63 percent to 26 percent.

Among those who feel they will be worse off -- a substantially larger group and one that would be expected to be strongly influenced by a campaign that attacks inflation -- Carter is preferred by 54 percent to 29. There is a difference, to be sure by only a small one.

The result for Reagan is in sharp contrast. To begin with, he is viewed as more likely to be successful in coping with inflation than is Carter.

One question in the poll asked: "Which one do you think would do best at seeing to it that your dollar buys more in a year or two than it does now -- Carter or Reagan?" By 48 percent 32 percent, those interviewed chose Reagan. The other 20 percent either thought there would be no difference between the two or voiced no opinion.

When pitted against Carter in a trial heat among registered voters in the poll, Reagan trailed Carter overall by 51 to 42 percent. Among those who think they will be better off financially next year, Reagan was behind by 62 to 34 percent. But, in contrast to Kennedy, among those who fear they will be worse off Reagan edged Carter, 47 percent to 45.

Before the 1980 campaign began, inflation was expected to be the number one issue. The seizure of the American Embassy in Tehran on Nov. 4 changed that.

Inflation clearly is the most important personal concern to a great many Americans and it has been spoken about much in the campaign. In that sense, it has been an issue.

But it has played a minor role until now as a voting issue -- less important, for example, than people's views of Kennedy's character -- and far less important than the hostage crisis.

The new Post poll seems to show that inflation is assuming the role that had been predicted for it for many months: that of a major voting issue in the campaign.

The poll contains evidence that the damage of inflation in recent months is more psychological than actual. That is, it suggests that while people now are much more worried about the future, their actual experience in coping with inflation is no worse now than it was a few months ago.

In a January poll and again in April, The Post asked whether people have had to make major sacrifices because of inflation, or make some sacrifices; whether they haven't had to make sacrifices yet but would soon, or whether inflation would not force them to make any sacrifices.

The findings in the two polls were exactly the same: 61 percent in January and in April said they had made at least some sacrifices; 30 percent said they would be forced to make sacrifices soon, and between 7 and 8 percent said they felt themselves to be inflation-proof.