Juan Williams' "Is Jesse Jackson Really Good for Blacks?" {Outlook, May 31} overlooks the important reality that white political candidates at every level, especially where blacks are in the minority, realize: concessions to blacks are the most expendable after the election is over and when the real political pie gets cut.

Having been an elected official (in Pittsburgh) and a journalist, I can cite numerous examples. When blacks in Chicago supported Jane Byrne over Michael Bilandic for mayor in 1979, what did it get them? In 1978, Republican Richard Thornburgh defeated Pittsburgh Mayor Peter Flaherty for Pennsylvania's governor by garnering over 35 percent of black Democratic voters. After Mr. Thornburgh's two terms were up, blacks could point to very few promises kept. The same could be said of the Eisenhower presidency and many other local and national campaigns in which the black vote was crucial.

So the average black adult, already a veteran of the plight of surviving in white America, understands that Frederick Douglass was right when he said that "power concedes nothing without a demand." A vote for Jesse Jackson is their way of telling the Democratic Party that if Jesse Jackson is not treated fairly and the promises he extracts for his delegate support (which will be considerable after the March 8, 1988, "super primary") are not kept, then they will either vote for the Republican candidate or, more likely, not bother to vote at all.

Either way, the Republican candidate will win. Ask George McGovern, Hubert Humphrey or Walter Mondale. DENNIS SCHATZMAN Silver Spring

I commend Juan Williams for his courageous commentary "Is Jackson Really Good commend Juan Williams for his commentary, for which he will probably receive a lot of criticism, especially from supporters of Jesse Jackson. Although I think he warns of dangers that are somewhat exaggerated, Mr. Williams deserves credit for raising issues that should be considered in assessing Mr. Jackson's second candidacy.

As Mr. Williams points out, racism poses a major obstacle for any black presidential candidate in America. However, it is not necessarily accurate to say about Mr. Jackson that, as his spokesman reportedly said, "If he were white, he'd be president."

Mr. Jackson has negatives with voters, even blacks, that cannot be totally dismissed as racism. In particular, voters prefer presidential candidates with experience as elected government officials, a qualification that Mr. Jackson is lacking. Historically, only members of Congress, governors or generals have ever been elected president.

By that standard, there are several black Democrats who are presidential prospects. They espouse the same views as Mr. Jackson but might be better able to put together a winning campaign, a true "rainbow coalition."

As a top leader in Congress with broad support, Rep. Bill Gray of Pennsylvania would be at the top of my list. However, as Mr. Williams argues, a Jackson candidacy discourages other black politicians from running, even someone with a better chance of winning. And if Mr. Jackson loses in 1988, will he run again in 1992? Will he continue to run indefinitely? Ironically, that would hurt the chances of a black person's becoming president. SKIP KELLY Washington