The poll data in the accompanying article, based on interviews with a sample of 1,280 people, are subject to a theoretical margin of error of about 3 percent for figures that apply to the full sample and a slightly higher margin of error for figures that apply to subgroups. The sample's characteristics of age, sex, race and education were weighted to match those for the nation at large as reported by the Census Bureau.

THE DEMOCRATIC Party appears to be unusually strong going into the November congressional elections, according to the findings of a national Washington Post poll.

Since the beginning of this century, the party that holds the presidency has lost an average of 34 seats in the House of Representatives in all off-year elections. This year, the poll suggests, such losses appear quite unlikely.

Democrats are seen by those polled as better able than Republicans to handle virtually every national problem; key voting groups such as independents and likely new, younger voters say they are leaning heavily toward Democratic candidates. Nationwide, registered voters say they prefer Democratic congressional candidates in their districts by a margin of 52 to 28, with 20 percent undecided.

That landslide proportion, of course, represents overall national sentiment and is not instructive in gauging the outcome in individual districts. It fails to take into account Republican strongholds or particularly attractive new Republican candidates.

The poll, therefore, cannot be used as an indication of how many seats the Democrats may lose or the Republicans gain, or vice versa.

It does, however, suggest that the Democratic Party nationwide has held onto the bulk of the gains it made in 1974, when, in the wake of Watergate, the Republicans lost 48 House seats.

In September of that year, the Harris Survey reported Democrats holding a 55-31 edge in the upcoming elections, almost exactly the proportion uncovered in the current Post poll. Party preference in the two polls was strikingly the same in big cities and suburbs, small towns and rural areas and for voters in various age classifications - a further suggestion that Democrats may be holding onto what they gained in 1974.

Pollster Louis Harris noted at the time that the most decisive shift came among independent voters who had gone for Republican candidates previously but were learning to the Democrats by a 48 to 25 margin in September 1974.

With the heavy edge in party affiliation that Democrats hold over Republicans, the only chance for Republican candidates in many districts lies in capturing the bulk of independent voters. But there are few if any signs of that happening. This year, with the Democrats in power, independents in the Post poll said they were leaning Democratic by a margin of 43 to 38, very close to the 1974 proportions found by Harris.

Inflation and Tax Issues

THE POST POLL was conducted by telephone from Sept. 7 through Sept. 17. Interviewed were 1,280 people who said they were registered voters, and 476 other adults nationwide. (Only the registered voters are included for purposes of analysis in this article.)

When asked what they considered the nation's most important problem, 50 per cent volunteered inflation, or the high cost of living, and another 6 per cent said taxes.

Republicans are running hard on these issues. The center-piece of many Republican campaigns is the Kemp-Roth bill to cut federal income taxes by 30 per cent across the board over the next three years.

When given a capsule description of the Kemp-Roth bill, 59 per cent of those polled said they would favor it, 31 per cent said they were against it, and 10 per cent were undecided. But when those who listed taxes as the nation's main problem were asked which political party was better able to handle the issue of taxes, the Democrats came out ahead, 39 to 22, with 34 per cent unable to pick one party over the other.

On inflation and the cost of living, 32 per cent of all those interviewed felt the Democrats were better able to handle the problem, 25 per cent the Republicans. A full 43 per cent couldn't choose between the parties.

Among independent voters, 57 per cent saw no difference between the parties in their ability to cope with the high cost of living. The rest were tightly divided, with 23 per cent favoring the Republicans and 20 percent the Democrats.

Consequently, while the high cost of living and inflation may be a vital concern to them, most independents do not regard it as a voting issue, one that they see as pushing them toward candidates of either party. They appear to the picking candidates for other reasons, and leaning heavily Democratic in the process.

Many political scientists and politicians believe that the state of the nation's economy is the single strongest indicator of the results of off-year congressional elections. If that is correct, the main hope for Republicans may lie in their ability between the time of the poll and Election Day to make the cost of living and inflation into a voting issue that will work for them, especially among independents.

As things stand now, Republicans hold the edge over Democrats on only one issue tapped by the poll - crime - and their edge on that issue is miniscule among the 7 per cent who listed crime as the nation's number one problem. On all other issues, the Democratic Party was seen as more able than the Republicans.

The poll also suggests that Democrats are favored heavily among likely new voters: people under the age of 30 who did not vote in 1976 but who say they are registered now and will probably vote or are certain to vote. While a good number of them may not follow through on their intentions, many others will, and, as a group, they say they are learning Democratic by a 64 to 21 margin, with 15 per cent undecided.

One other factor favoring the Democrats is a development that occured in the days following the Post poll: the sudden sharp rise in popularity of President Carter after the Camp David Middle East summit. Many political scientist feel that the fate of congressional candidates in off-year elections is at least in part tied to a president's "approval rating" as measured by the Gallup poll just before the election.

The Post's poll on issue dealing with Congress was complete just as the Camp David summit was concluded, and just before most of the rise in Carter's popularity. It is reasonable to assume that Democrats would be even more heavily favored in any new poll of congressional voter preference, reflecting the president's higher approval rating.