On a day when President Carter's consumer price index soared to politically horrendous heights, Sen. Edward M. Kennedy (D-Mass.), who has tried to build his campaign upon a foundation of economic leadership, gave the fact only modest mention.

The issue of the economy, which Carter advisers once feared mightily, has not caught on in New Hampshire.

Kennedy's closest advisers have contended that the economic issue has not proved decisive because it has been forgotten in the foreign policy crises of Iran and Afghanistan.

That may have been a large factor, but it is also true that Kennedy has failed to make the economy the burning issue he once hoped it would be not in the opening days of his presidential campaign, and not in the days following his Georgetown University speech in which he sought to resurrect his campaign, which had been crippled in the caucuses of Iowa.

At a meeting of senior citizens here today, Kennedy ignored the new inflation figures, which offer statistical buttressing of his lagging campaign. iLater, at a rally of cheering high school students, Kennedy devoted a few sentences to the latest price index, but promptly overshadowed that message with a long, bellowed blast at the gun lobby.

There is evidence that the economic issue could have been the dangerous soft center of Carter's support, which has, even at its best, been shown to be lacking in strong feeling and commitment in New England.

Consider the latest findings of the University of New Hampshire poll. This survey which showed Carter leading Kennedy by a decisive 47 to 29, also showed that 80 percent of the people interviewed disapproved of the way the president has handled the economy. The president's performance in office was rated favorbable by 35 percent, according to Robert E. Craig, codirector of the survey.

Poll data gathered by The Washington Post and other organizations show that inflation -- generally regarded as Carter's single greatest vulnerability before the campaign began -- is now virtually dormant as a voting issue.

Last summer and fall, Post polls at the time showed, people who felt they were suffering because of inflation were greatly inclined to oppose Carter's reelection. The minority of the public that felt it was not being hurt by inflation tended to support Carter.

In a Post poll last month and in other more recent polls, however, that has not been the case. An increasing number of people feel they are being hurt by inflation -- but they nevertheless tend to support Carter in proportions almost equal to those reported by people who feel they are not being hurt by inflation.

The president's deputy campaign manager, Christopher Brown, who is in charge of Carter's New Hampshire effort, offers his own, clearly pro-Carter explanation. "I think the economy is a factor," he said, "but the people have decided they do not agree with Kennedy's solutions." Carter campaign manager Tim Kraft added, "People just don't think Kennedy can solve their problems."

Part of the reason Kennedy has not been able to cut significantly into Carter's vote with criticism of the economy may stem from the fact that New Hampshire voters have been spared from some of the year's economic hardships.

It is true that the price of heating oil has soared, but the scarcity that was feared for this winter never materialized, largely due to an unusually mild winter, but partly due to the administration's efforts to assure that there would be adequate supplies of heating oil in the New England states, where the weather is cold and the primary elections are early.

New Hampshire also has been spared the unemployment problems. Its rate of joblessness is unusually low.

But despite the crises of foreign policy, the mildness of the winter and the low unemployment rate, Kennedy's hopes of building his campaign around dissatisfaction with the Carter economic record has also been marred by his own campaign performance.

The senator and his advisers had hoped that his speech at Georgetown University after the Iowa caucuses would once again focus public attention on the Carter administration's economic record and his own solution, which calls for a freeze on prices and wages.

But in the weeks that followed, Kennedy drowned out his own message. He issued daily colorful attacks on what he calls Carter's Rose Garden strategy. He challenged Carter to debate him and chastised the the president's failure to accept. And he issued harshly worded critcisms of Carter's handling of the crises in Iran and Afghanistan.

Most of his speeches also carried criticisms of the Carter economy, but it was the other more colorful and combating comments that drew the coverage of the television and radio networks and the printed press.

Some advisers, including Kennedy's New Hampshire aide Dudley Dudley, blamed the media for not having carried the message of Kennedy's criticisms on the economy. But, in fact, Kennedy often spoke of the economy rather briefly, dwelling on the other issues instead.

Yesterday's consumer price index showed a rate of inflation that was the highest since August 1973, when Richard M. Nixon was president.

"I believe that this means the president of the United States is playing a losing hand in fighting the battle against inflation," Kennedy told a rally at the West Senior High School. "I believe the president . . . is ignoring the important warning signs of our economy. And I believe the only step that can effectively break the back of inflation in our country is a freeze on prices in our nation so that we can effectively stop inflation. . ."

This said, Kennedy launched into his impasioned attack on the gun lobby, which has set its sights on his defeat. He gave no explanation of how his policies would cure inflation in ways that Carter's have not.

Nor did he cite the fact that Carter's former director of the Council on Wage and Price Stability, Barry Bosworth, has recently spoken out in favor of wage and price controls. Nor did he mention that the man who is regarded by many as the leading economist on Wall Street, Henry Kaufman of Salomon Brothers, had just the day before called for "a temporary wage and price freeze."

While Carter's political advisers concede that the issue of the economy could still cause political problems, they say they do not expect today's consumer price index report to significantly affect the results of Tuesday's primary election in New Hampshire.

"I doubt that something that comes just four days before an election can have that much impact on the results," said Christopher Brown. "I mean, the fact that inflation is high is not anything new. People get direct mailings every month that remind them of it. They are called utility bills."