Gary Hart, a forgiving fellow, is moving with measured strides to give the national electorate a second chance. His first step is to deny Colorado a third chance. Hart, a prudent fellow, is the second Democrat to make much of announcing what he is not going to do.

All our leaders are, of course, brave, resourceful and gallant, but Kennedy and Hart made withdrawal statements that the Food and Drug Administration should label "Do Not Swallow." Kennedy's sufficient but unspoken reason for not running for president is that he cannot win. Hart's unspoken reason for not running in Colorado is that victory would be problematic, and even if he won with, say, 52 percent (about 2 percentage points better than he did in 1980), such narrow escapes in one's own state do not impart much momentum. (His 1974 victory came over an incumbent, Peter Dominick, who was incapacitated by the medication he was taking for the illness that was to kill him.)

Hart has often been a valuable senator, as when he opposed the stampede in support of the Gramm-Rudman folly. He saw the unseemliness of senators and congressmen constructing a mechanism to insulate them from accountability for painful budget-cutting choices. To help them keep office, they have diluted the dignity of office; to preserve personal power, they have yielded institutional power, wholesale.

Hart says, "I've never seen politics as a career." But he plans to leave the presidency after two terms at age 59 never having had any career but politics. Kennedy's withdrawal casts Hart in the dreaded role of front-runner. Being the front-runner is nasty work, but someone must do it, so why not someone who got 1,200 delegates last time? Besides, front-runnership is a function of name recognition. Two years before the 1960 election, the leading Democratic contenders were Adlai Stevenson at 29 percent, John F. Kennedy 23 percent and Estes Kefauver 11 percent.

What one Democratic professional says of another possible presidential candidate (Rep. Richard Gephardt of Missouri) could be said of Hart: "There is no MSG in the guy -- no flavor." Yet Hart's personality has, for many people, a kind of disagreeable bite. He makes many people vaguely uneasy. A comfortable feeling about a candidate may be an inappropriate criterion for voters to use, but Hart may be exactly the wrong kind of candidate for the first post-Reagan election, Reagan having accustomed the country to an easy intimacy, the old-slipper feeling, with its head of government.

The attributes that suit Hart to the Senate may incapacitate him as a presidential candidate. He is cool, technical, analytical, utterly unlike the man who in a span of 48 months carried 93 states.

Hart says e is "shy," an odd description for a fellow who has spent years pressing himself on the public without the motivation of any pressing agenda of the sort that has animated Reagan. However, Hart has enough self-knowledge (and, perhaps, plural selves) to be referring to something as real as shyness: it is an inner motor that seems disconcertingly unconnected from public passions. What derailed his express in 1984 was the voters' unarticulated worry that Hart (like Johnson, Nixon and Carter) might be working out private turmoils in public action.

His vulnerability to the question "Where's the beef?" was inherent in his "new generation" nonsense. Any campaign with a "generational" theme is apt to be intellectually vacuous in its attempt to make a virtue of mere membership in a particular demographic group. Worse, a "generational" theme adopted by someone who came to political consciousness in the 1960s is apt to express the insufferable narcissism of a small portion of that generation who hink they experienced history more intensely than anyone ever did before. That thought must amuse older Americans who were not at Woodstock but were at Omaha Beach, and in the Depression.

Besides, a generational appeal can, in time, turn and bite the ankle of the person making the appeal. Ronald Reagan, the oldest person to begin a presidential term, did not enter politics until he was 55. Of the score or so persons now mentioned as candidates in both parties, relatively few (such as Bush, Dole, Baker, Kirkpatrick) are over 55. Hart will be 51 in 1988, and will want to change the subject from age to anything else.

Kennedy's absence will help. Were Kennedy going around the primaries and caucuses being Kennedy, anyone else could claim to be, by comparison, a centrist overflowing with new ideas.

With Kennedy out, Hart can concentrate on stigmatizing Mario Cuomo as the person who has caught Kennedy's falling flag as the Last New Dealer. If, that is, Hart can bring himself to think of politics as a career.