Paul Kirk's refusal, moments after being selected Democratic national chairman, to ratify the choice of the party's Black Caucus for vice chairman was the best thing that's happened so far to the Democrats this year. And, though you wouldn't know it from Jesse Jackson's cries of anger, it's the best thing that's happened for the cause of blacks in politics.

It's good for Democrats because it strikes a blow at the party's whole gaggle of caucuses by reducing the power of the most visible and powerful of them. They don't have an automatic right any longer to name officers who will in turn speak for the national Democratic Party. All the Democrats on the national committee have, sensibly, reserved the power to determine who will speak for them.

It may not be so clear that the defeat of theBlack Caucus's choice, Gary Mayor Richard Hatcher, is also good for blacks in politics. But it is, because it reduces the power of those who court all-black constituencies with more-militant-than-thou appeals and redirects black politicians' attention to the more useful question of how to go about achieving political goals in a nation that is 88 percent non-black.

That was apparent, evidently, to many members of the Black Caucus themselves. They endorsed Hatcher, the incumbent vice chairman, by only a 32-25 vote -- the equivalent of the message to the convalescing union business agent that "the executive board wishes you a speedy recovery by a vote of 9 to 6."

They had good reason to distrust Hatcher. As vice chairman of the party in 1983, he endorsed the Hunt Commission delegate selection procedures as fair. As a Jesse Jackson backer -- he nominated Jackson at the San Francisco convention -- he shamelessly turned around and called the Hunt Commission reform biased. Politicians of all races tend to distrust colleagues who go back on their word, refuse to live up to their commitments and attack the legitimacy of organizations whose leadership positions they hold.

But Hatcher has spent his entire political career appealing to blacks only. He has sought and won only black votes in his five victories as mayor of Gary, and the last three times, as the novelty of having a black mayor wore off, he has no longer won all blacks' support. Operating in one of the most racially polarized political environments in America -- he is hated in the white factory towns and suburbs around Gary -- he has not had any ambitions to seek office in larger constituencies in which, in other circumstances, his honesty and his high competence might make him an attractive candidate.

The new vice chairman, Roland Burris, has made his career in majority-white constituencies. He is from downstate Illinois, not Chicago; he was elected state controller by one of those huge margins voters give downstate Democrats who make a name for honesty and competence. He ran for the Democratic Senate nomination in 1984 and ran second in a field of four competent candidates, beating the party's 1978 nominee, who spent freely of his own money, and a Cook County state senator who had the endorsement of the Democratic organization.

Running on the same day as the presidential primary, Burris won more votes and got a higher percentage than Jesse Jackson in Illinois. And he won it in a race that was for keeps: Burris had a real chance for the nomination, and the nominee in turn had a real chance to win (as the winner, Paul Simon, did). "I assume Roland has his own constituency," Jackson said angrily after the vote. He does, and it's larger than Jackson's.

If there are to be more successful black politicians in the future, their careers will look a lot more like Burris' than Hatcher's, because blacks have already won almost all the black- majority districts. And if black voters are going to be represented in the councils of the Democratic Party, they're going to have to be represented not just by members of black caucuses, but by all party members, all of whom have or should have an interest in fair representation of blacks. The members of the Congressional Black Caucus represent only 23 percent of American blacks.

The Democratic Party's Black Caucus, like other Democratic caucuses, has an incentive to demand what the party and the public don't want to give. Otherwise why have a caucus? Caucus members are in competition to see who can come up with the most unpopular demand. Accepting such demands, or even meeting them halfway, is not in the interest of the whole party. For instance, in recognizing a "differently abled" caucus -- the handicapped -- the party has managed the not inconsiderable task of making unattractive a cause to which people are naturally sympathetic. Kirk's refusal to let the Black Caucus choose the party's vice chairman is a sign the Democrats may finally be moving away from caucuses and toward a potential majority coalition.