You're Fritz Mondale, and the news lately has not been good. Yes, you probably "won" the Kansas City debate, but that, under the unpublished rules of political expectations, does not mean that Ronald Reagan "lost." By now you have probably concluded a couple of hundred times that, last Sunday night, you should have confronted Reagan by quoting from his 1960 letter to Richard Nixon in which Reagan -- who this autumn has been all but canonizing John Kennedy -- castigated the late president's campaign as "old Karl Marx." We'll never know just how badly Reagan might have stumbled on live, national TV.

But now the question is no longer what Fritz Mondale ought to have done. It is instead what he ought to do in the last 10 days of what will probably be his last national campaign. What does he choose to say, and to whom? What message can most help other Democrats on the ballot and still preserve the now slender hopes for presidential victory? What does Mondale want to say to posterity about what he stood for in 1984? How does he want to write his political epitaph?

These are painful questions for anyone to be asked, let alone to answer. But in the last twoweeks of any campaign when a candidate trails his opponent by a margin (12 percent) three times larger than the undecided (4 percent), the possibility of defeat cannot be ignored.

Conversations with longtime Mondale supporters and with Democratic politicians, who remain overwhelmingly pro-Mondale in spite of the bleak outlook, have helped in drawing up a list of possibilities. In the judgment of other Democratic campaigns that have been saddled, this fall, with their nominee's acceptance speech pledge to raise taxes to pay off the federal deficit, the very best thing Fritz Mondale could immediately say would be: "As president, I'll raise your taxes. And so will Ronald Reagan; make no mistake about it. He won't tell you. And I sincerely wish I hadn't." Mondale's convention candor failed to achieve its intended effect of placing an evasive Reagan on the defensive. Instead, other Democrats have found themselves on the defensive, and Reagan has been able to make the issue into an applause line.

If those Democrats running this fall had another wish, it would be that the nominee direct his attention to Democrats in these closing days. One professional urges that Mondale, now that his debate appearances have raised his personal ratings to solidly positive, scrap all 30-and 60-second TV commercials and purchase in their place five-minute blocks of network time in which to make a series of mini- speeches to the nation.

Suggestions of topics for these single-subject speeches vary. Mondale is urged to talk about whose finger ought to be on the nuclear button, because this is, as a prominent Democrat puts it, Reagan's one "de-teflonized" issue where the president must accept full responsibility and cannot announce "an immediate investigation to fix responsibility." Mondale might also speak about his commitment to standards of excellence and his belief that Americans can be both affluent and altruistic, both fiscally responsible and socially responsible, competitive and compassionate.

Mondale would acccomplish nothing by throwing raw meat to his true believers in the form of more Reagan-bashing. But he could profitably raise questions about Reagan's plans and emphasize how they have no relation to either solving serious problems or to reality.

Budget deficits will not be wished away. Toxic waste is a threat to public health and cannot be cleaned up at no cost, with no leadership. Taxes will be raised, and programs will be cut; it's inevitable. The question for voters to face is: Do you want Democrats or Republicans making those cuts and looking out for working people's interests?

As a political epitaph, Fritz Mondale could do worse than to choose words similar to those that were the favorite of a fellow Minnesotan who had the bad luck to run in another non- Democratic year. Hubert Humphrey said: "The moral test of government is how it treats those who are in the dawn of life, the children; those who are in the twilight of life, the aged; and those who are in the shadows of life, the sick, the needy and the handicapped."

Of course, Mondale could also win.