Two thumping facts about New Hampshire's primary prove its capacity for seriousness and silliness. The first fact is that since 1952, everyone elected president has won it. The second is that it also has been won by Estes Kefauver (1952) and by the U.S. ambassador to Saigon, Henry Cabot Lodge, who in 1964 did not set foot in the state while a few young people rustled up 33,000 write-in votes to defeat two heavy hitters, Nelson Rockefeller and Barry Goldwater.

Serious or silly, New Hampshire gets attention. The 1984 Democratic nomination contest continued all the way to California in June. But Prof. William C. Adams notes that the Pennsylvania, Ohio, Illinois, North Carolina and California primaries, in which 8,403,000 Democrats voted, together received less media attention (in NBC, ABC, CBS and New York Times campaign stories from Jan. 1 to June 10) than New Hampshire's primary, in which 101,000 Democrats voted.

Yet in spite of the attention lavished on New Hampshire primaries, there is much misunderstanding of what has happened in them. In 1972, in spite of the crying episode, Edmund Muskie actually beat George McGovern 46 percent to 37 percent. In 1968, in spite of the Tet offensive, Lyndon Johnson, whose name was not even on the ballot, won because 27,520 people took the trouble to write him in while Eugene McCarthy, whose name was on the ballot, was getting 23,269 votes.

Furthermore, although New Hampshire Republicans are conservative, three ''Mr. Conservatives'' have lost the primary: Robert Taft to Eisenhower in 1952, Goldwater, and Ronald Reagan by 1,587 votes to Gerald Ford in 1976. Those may have been the most consequential 1,587 votes in New Hampshire history. Had Reagan beaten Ford there, he almost certainly would have then won in Florida and been nominated.

This year, New Hampshire's grisly role as guillotine may highlight an interesting geographic fact. By 11 p.m. Tuesday, the Democratic Party's two westerners, Bruce Babbitt and Gary Hart, probably will be gone. If George Bush loses (and if he really is a Texan rather than, as he says this week, a New Englander), the Republican westerner may be on his last legs. So, too, may be two Republican easterners: Jack Kemp and Pete du Pont.

Now, take a map of America and put a pin in central Missouri. Around it draw a circle with a radius covering 300 miles. Within the circle you will find St. Louis, Chicago, Makanda, Ill., Carthage, Tenn., and Russell, Kan. These are the home towns of Dick Gephardt, Jesse Jackson (to the extent that a human sirocco has a home town), Paul Simon, Albert Gore and Bob Dole, respectively.

Although one of these candidates, Jackson, is outside the political mainstream, the circle suggests a tendency: a certain middlingness is asserting itself. Less than four years ago, some despairing Democrats thought that was not desirable.

Shortly after the 1984 loss, the fourth in five presidential elections, some Democrats argued that rather than compromise its principles, the party should reconcile itself to a politically reduced but morally shimmering role. As Tom Wicker reported the argument, it was that the party should stop hoping to win majorities.

Instead, it should concede to the Republican Party the role of the ''party of government'' and should settle for the role of ''party of access'' for minorities and various ethnic social and cultural interests. The Democratic Party would be the place where ''the voiceless find a voice'' and their pressure ''can be transmitted outward to the other party and to government.''

In response, Prof. Sam Huntington noted that the concept of a ''party of access'' at least implicitly acknowledges that a party of the American left cannot be a majority party. Furthermore, the ''party of access'' concept, although expressing a democratic pessimism, also involves moral self-congratulations: the American majority is implicitly condemned as morally inferior.

But Democrats need not despair. An ABC poll shows that after seven Reagan years, Democrats still retain a 35-to-28-percent edge over Republicans in party identification. Furthermore, in a ''generic'' race, polling an unnamed Democrat against an unnamed Republican for president, the word ''Democratic'' won 46 to 43. And the candidates who are spared New Hampshire's guillotine will benefit from ''de-dwarfization,'' the acquisition of stature by survival.

If in spite of its rules and its activists' instincts the Democratic Party can come up with a nominee whose views are broadly congruent with those of the voters who live in the circled region, the party will be back standing, if not necessarily tall, at least upright.