During his 1984 campaign for the Democratic presidential nomination, Sen. Gary Hart (D-Colo.) was frequently accused by critics of aping the movements and mannerisms of John F. Kennedy. But this week, in a serious speech on patriotism he gave in Boston, Gary Hart did sound a lot like Kennedy. Asserting that "true patriotism is . . . built upon a sense of community," Hart argued for the creation of "a new system of national service -- including both military and non-military opportunities -- (that) will ask young Americans to return some of the advantages and investments they received from our society." Careful to pick his adversaries, Hart contrasts his policy not to Ronald Reagan's but to that of "the Republican right wing," which, according to Hart, says, "We don't owe our country anything; that citizenship, opportunity and patriotism are free."

For good reason, recent Democratic candidates for national office have been regularly accused of clumsily coddling every semi-available constituency (recall last year's New York presidential primary, when Hart and Mondale were practically hiring the moving vans to transport the U.S. Embassy's furniture from Tel Aviv to Jerusalem). This week Hart did just the opposite. In a city that is the favorite of many Yuppies and more than a few pacifist- isolationists, he boldly challenged his prime constituency, the young; and he did so in the capital of New England, where he carried all six 1984 primaries and where conspicuous opposition to the American military has boosted more than one aspiring politician's career.

Two days after the Boston speech, Hart talked about an apparent U-turn in his thinking from his Senate vote against requiring 18-year-olds to register with the Selective Service to his current call for national sevice for all "with no exemption, no deferments." He admits that "the latent idealism" he believes resides in Americans "has been essentially untapped since the '60s" by political leaders, including himself. Hart clearly understands that any time you have a broad-based military service (which would put in potential jeopardy the sons of Americans with both affluence and influence), the more restrained U.S. policy would almost certainly be.

In a week when the Washington talk has been of public deficits and drastic budgets cuts, Gary Hart, as yet, has no price tag for his national service plan. But Hart has challenged his party, which has spoken much about "fairness" but has been publicly indifferent to Reagan's policy. That policy essentially frees from military obligation those fortunate Americans with the means and the opportunity to go to college.

Hart has challenged the young, about whom so much has been written and so little is kown. And he has directly confronted the Reagan administration's version of "painless patriotism," which calls for our sacrifice by paying for the doubling of our defense budget by accepting one-third cuts in our taxes. Gary Hart has said that citizenship requires us to pay a price, to bear a burden.