Washington — There are two forces tugging and pushing inside the Democratic Party as the 1984 primaries draw nearer, and the result could be one of the most tantalizing presidential contests in years. Those forces are:
* A strong desire, deepened by four years of conservatism in the White House, to elect a president who captures the spirit, the heart, the compassion of the Democratic, Rooseveltian tradition.
* An equally urgent need to avoid defeat, to avoid the recent problems that have sent the party careening to defeat in every presidential election but one since 1964.
Those two goals may be in conflict in 1984.
There is little doubt that Walter Mondale stands front and center among Democratic regulars as the torchbearer of the party's long-held values, the values that grew out of the New Deal and Great Society years. The polls show it. Party leaders say it, both publicly and privately.
But the polls also tell something else. And if modern-day politicians have learned anything, it is to take the polls seriously. Month after month, Gallup, Harris, and other pulse-takers find that John Glenn would be a stronger Democratic candidate - the man with a better chance to defeat President Reagan.
The latest Garth Analysis, produced by political strategist David Garth of New York, shows how important the final choice could be for the Democrats.
Mr. Garth finds that in a trial heat, Glenn beat President Reagan by an impressive 47 to 41 percent in September. On the same day, Reagan whipped Mondale 44 to 42.
Similar results are found by other polls. Gallup, for instance, recently showed Glenn drubbing Reagan 48-42, but Reagan edging past Mondale 47-44.
Glenn's strength with the man-in-the-street is not just preventing Mondale from running away with the Democratic nomination. It also is keeping the race open longer for dark-horse contenders like Alan Cranston, Gary Hart, Reubin Askew, Ernest Hollings, and George McGovern.
If that weren't enough, the Democrats have something else to worry about: Month after month, President Reagan is looking stronger.
Every time the unemployment rate drops, new-car sales rise, the stock market rallies, or a factory reopens, the President's public support grows a little stronger.
The average American, observes Donald Ferree, associate director of the Roper Organization, isn't very interested in economic theory, whether it's Reaganomics , Keynesian, or New Deal.
''The vast bulk of them just want something that works,'' he says. And right now people can see what is happening: Inflation is down and is staying down; the unemployment rate is high, but dropping; the stock market is breaking records.
When things go badly, it's usually the president who gets the blame. And when they improve, he gets the credit. That is what is happening now, Mr. Ferree says.
There's one other bit of good news for Mr. Reagan.
When Korean Air Lines Flight 7 was shot down six weeks ago, Reagan avoided any bellicose response. As one pollster puts it: ''His manner was presidential.''
This did two things. It increased support for Reagan's defense policies. And it made him look less like a warmonger - an image which has hurt him especially with women.
The results have been impressive. The President's approval rating, according to the Harris poll, has risen from 38 percent in January to 45 percent in June and to 56 percent in September.
Recent debates among the seven Democratic candidates - in New York City and Cambridge, Mass. - have done nothing to make the choice easier for the party faithful.
In New York, front-runner Mondale, who is currently the choice of about 37 percent of party supporters, according to the Gallup Poll, performed with little fire or enthusiasm, a number of observers agreed.
Conversations with Democratic Party activists after the debate indicated that most felt Senator Hollings (who is backed by only 1 percent of Democratic voters) came off best. Also doing better in the debate, many suggested, was Mr. Askew (who has only 3 percent support) and Glenn (backed by 26 percent of all Democrats nationwide).
Why does Glenn defeat Reagan in test-run polls? And why is he stronger than Mondale with voters outside the Democratic Party?
The Gallup Poll tried to determine the reasons for Glenn's strength by asking voters to name each candidate's strengths and weaknesses.
Gallup's findings are too long and detailed to include here in full, but a few of them are revealing.
Reagan is seen as ''bright and intelligent'' by 53 percent of US voters; Mondale gets a similar description by 56 percent. But Glenn, perhaps due to his astronaut background, is well ahead at 65 percent.
Other readings also show Glenn's strengths:
Which person is ''likeable''? Reagan, 50 percent; Mondale, 50 percent; Glenn 63 percent.
''High moral principles''? Reagan, 50 percent; Mondale, 49 percent; Glenn, 63 percent.
''Decisive, sure of himself''? Reagan, 48 percent; Mondale, 41 percent; Glenn , 53 percent.
''Exceptional ability''? Reagan, 35 percent; Mondale, 32 percent; Glenn, 41 percent.
Mondale comes out clearly ahead of Glenn in only one major category: ''sympathetic to the poor.'' On that issue he gets a 44 percent rating from the public, while Glenn rates only 37 percent, and Reagan trails at a mere 21 percent.