Another go at the often-asked question, Why do intellectuals tend to be liberal? Miss Mannes's answer may not be especially strtling, but she and her host strike sparks off each other in delightful ways. And, in retrospect, an exchnage like the following illuminates what would be different about the Reagan Presidency. MM: "You know, there's been awfully little fun in conservative and Republican politics, terribly little fun." WFB: "You don't think Herbert Hoover was fun, huh?" MM: "Not riotously, no....I think that the gaiety, the fun, the vitality, the feeling of adventure has resided far more, certainly in the last decades, in the Democratic end of things than in the Republican."