Straight talk

''Relax. The pressure of a tough series can add a tightness to your smile,'' the public would advise Sunday night's presidential debaters. ''We're not all cranked up, mad at each other, broke, in the dumps about humiliations abroad. This is not an angry election. We've some differences we'd like to hear you talk about. But there's more that unites than divides us in this election. You do us no favor by assuming an animosity we do not feel.

''We're looking to the future. This may sound odd, when for the first time we have more senior citizens than teen-agers in America - but who says looking ahead is a characteristic only of youth? We learned with the baby-boom experience, through the conflict of the '60s and '70s, that a youth wave alone brings no panacea or sense of direction to American political life. That generational conflict has passed. One of you is a senior incumbent whose strongest support comes from the youngest voters. Gains in political power for blacks, the Sunbelt, and more recently for women have put within sight much less conflict along racial, regional, and gender lines. The political process is progressing toward equality of opportunity, slowly perhaps in personal terms but quickly as measured by history.

''Mr. Mondale, think back to your party's July convention, the last time you pulled even with your opponent. The Democrats talked about the extended American family, about the ideal of inclusiveness. Each of the four active forces of the party in 1984 had its convention hour - minorities behind Jesse Jackson, the upwardly mobile young Democrats backing Gary Hart, the activist women rewarded with the nomination of Geraldine Ferraro, and the union and political establishment that backed you. Since then, you've really been functioning on only two of the four cylinders, the Ferraro and Mondale forces. You've seemed to retreat into a defense of the regions, industries, and interests that most resist economic change. That concedes to your opponent, the incumbent, the argument for change - at the same time he will take credit for the relative economic prosperity of the status quo. It's up to you to reassert your party's inclusiveness. You won't have Gerry Ferraro, Jesse Jackson, and Gary Hart in Louisville to help you out Sunday night.

''Mr. President, you have a lot of goodwill going for you. Setting out with a list of things to do, you followed up. On the economy, the arms buildup, and your overall comfortableness in the job, Americans give you high marks for leadership. But we want you to level with us, too. We're concerned about budget deficits. Your Treasury secretary says the administration would propose a new, flat-tax system next year. If the domestic theme of your first term was curbing the growth of federal spending, a second term will focus on federal revenue intake and reform. Where do you really stand on new taxes? Careful. We'll be listening for nuances.

''And on peace: The first debate is supposed to cover domestic affairs, but you can take the opportunity to talk about peace when asked about the fruits of your defense buildup, or if asked about leadership style. We'd really like to know what you learned about Mr. Gromyko and Soviet intentions. We don't want to hear what Secretary of State Shultz, or some nameless White House source, says you think about your first direct encounter as President with America's rivals. What do you think? When the issue is the prospect of the earth shaking beneath nuclear warfare, wasn't it rather late, your first four years winding down, for sizing up your adversary and looking directly into each other's eyes as you state positions?

''We're not interested in statistical quarrels, whether there are more or fewer poor, hungry, homeless, and undereducated in America now than four years ago. There are still too many left out of the general prosperity - both among the very young, especially men, and the senior, especially women. How will you help them?

''Religion: Is religion an issue between the individual and his government, or between the individual and his Deity? Is there room in a ''Christianized'' America, which some call for, for non-Christians and nonbelievers - or even all varieties of Christians?

''We don't care whether the race is close or not. Most of us won't keep score cards, as in that other series now going on. Ninety minutes isn't long for straight talk about leading our nation. We promise not to get bored.''