Marvin Kalb's first question to Democratic presidential candidate Paul Simon was a familiar one--how can a man who wears a bow tie, horn-rimmed glasses and two hearing aids be elected president?

Kalb's opening salvo sparked laughter from the Democratic Senator from Illinois and the rest of the Kennedy School audience during the sixth weekly "Candidates '88" forum, where style over substance continues to be a theme.

Kalb, who does not sport a bow tie, yesterday followed his usual tack in these hour-long interviews sponsored by the Kennedy School's Shorenstein-Barone Center for Press, Politics, and Public Policy of firing questions on a broad range of policy questions. But, as usual, the answers he got rarely went beyond campaign rhetoric.

Half of the six Democratic and six Republican candidates have already come to the Kennedy School in this 12-weekseries and the issues of character and personalstyle have dominated the forums as much as theyhave come to play a major role in the presidentialrace itself.

Kalb, director of the Shorenstein-BaroneCenter, bills the forums as "live, unrehearsedconversations with the major candidates" of bothparties.

But so far the impressions left by thebroadcasts, which are televised on PBS eachSunday, have been confined to the level of thecandidate's sartorial splendor and his ability toscore a quick comeback against Kalb.

The hard-nosed questioning by Kalb, a veteranreporter who was formerly NBC News's chiefdiplomatic correspondent, has touched on a widevariety of substantive policy issues. Yesterday hepushed Simon on his plans for the economy; lastweek he hammered away at Gov. Michael S. Dukakis(D-Mass.) on the issue of his inexperience withforeign policy.

But these tough, substance-oriented questionstend to get lost among the many personal queriesthat Kalb makes. On foreign policy last month,Dukakis was forced to admit he has never read anyof the major popular books on the Soviet Union.Simon yesterday called "Black Boy" by RichardWright his favorite book and in a previousinterview Republican candidate Pierre du Pont IVdefended his right to call himself "Pete."

When Kalb asked the Illinois senator about anNBC News debate among all 12 candidates last week,Simon responded with an attack on the number andformat of debates the candidates feel compelled toattend.

"We have too many [debates]," Simon said. "ButI have to go because the other candidates do."

But he added, "I much prefer a format like [theKalb program]."

Yet Simon, like the other candidates who havecome to the Kennedy School, rarely took advantageof the opportunity to give more than the usualpre-packaged answer.

When pressed by Kalb on his pledge to increasesocial spending programs at the same that he plansto balance the federal budget, Simon resorted tohis tried and true rhetorical formula, urging thecountry "to seize and create our own destiny."

Kalb may recognize this problem in his debates.Even as he jibed with Simon over bow ties andbooks, Kalb seemed to want to move away from thepersonal issues that have dominated the campaign.Before the cameras went live yesterday afternoonand before the former television journalist openedwith his question about hearing aids, Kalbreminded the Kennedy School audience to stay awayfrom "mushy" questions