You have completed five years of your Senate term, yet a third of the voters still don't recognize your name. You are being picketed by the anti-abortionists and pamphlets are appearing at shopping centers claiming that you, the junior senator from a jerkwater state, single-handedly gave away the Panama Canal. Half the phone calls to your office are from liberal campaign consultants saying you are in trouble and need their help.

A young Republican congressman, with family money and a voting record to the right of the Hapsburg monarchy, has just commissioned a poll to see how vulnerable you are. You've just caught your trusted administrative assistant copying his resume. Time to despair? Never. Just follow a few of the next three rules. Rule four: Sell Out on One Key Issue

You've been carefully compiling a record of quiet integrity and dedication to liberal principle. You're 47 years old; you can worry about the history books later. Right now you've got a family to support. In choosing an issue that will mark your accommodation to the world of practical politics, don't go off half-cocked and antagonize your traditional supporters. The AFLCIO will not take it kindly if you suddenly denounce labor law reform as a "naked power grab" by "senil union bosses."

Take your lead from Alan Cranston and Gaylord Nelson. Senate whip Cranston is one of those reliable senators who can be counted on to vote for the Panama Canal treaties, SALT II, and against a five-percent increase in the defense budget. Cranston is one of your standard liberal critics of the defense budget -- unless California jobs are at stake. Right before his last election in 1974, Cranston provided the key vote for the $250 million federal bailout of Lockheed. This time California defense contractors, particularly those at Rockwell International, will be reminded that he was one of a handful of Northern Democrats to support the construction of the B-1 bomber.

Nelson, that rugged outdoorsman, was the creator of Earth Day and has an almost perfect environmental record -- with one important exception. He parts company with the environmental movement over their demand for mandatory desposits on soda and beer bottles. The last time the issue came to the Senate floor, in 1976, Nelson voted against it. It is not coincidental that Milwaukee, the largest city in Nelson's home state of Wisconsin, is also the city that made beer famous.

Even George McGovern, representing the agricultural state of South Dakota, has moved away from the extremes of the nutrition movement he helped create. In August he introduced two key bills on food labeling and billed them as a way "to ease federal regulation." Earlier this year he surprised a hearing of his nutrition subcommittee by announcing that he had been guilty of giving fast food "a bad rap. The truth is that you may be better off nutritionally than you would at some gourmet restaurant." With the vice president for public affairs of McDonald's looking on approvingly, McGovern even derided a Broom Hilda comic strip that claimed that fast food is "something cheap with no real value." Rule five: Sell Indulgences to Those Who Oppose You on Moral Grounds

In politics, there are moral issues such as abortion, school prayer and obscenity. And then there are pocketbook issues like inflation, unemployment and tax cuts. Novices at running for cover will try to stress pocketbook issues and waffle on the moral issues. But the real pros will try a more sophisticated tack: standing firm on moral issues, while simultaneously supporting federal subsidies for their most zealous moral opponents.

Again it is Gaylord Nelson who demostrates how the game is played. Despite often voting against restrictions on abortion, Nelson is one of the few Senate liberals who has not been targeted by the antiabortionists in 1980. The secret is his firm support for tuition tax credits for Catholic parents with children in parochial schools. He calculates that most Catholics are more concerned about money in their pockets than about the moral dilemmas posed by abortion. This ploy was invented by Pat Moynihan of New York, one of the few Catholic senators with a staunch proabortion voting record.

No pro-gun control senator has ever had the gall to propose that federal money be appropriated for a National Riflery Hall of Fame, but George McGovern has been a loyal supporter of the federally subsidized civilian marksman program run in conjunction with the National Rifle Association. Rule Six: Use Your Family as Symbols

No one has ever followed this rule more slavishly, and more effectively, than Strom Thurmond of South Carolina. In winning reelection to the Senate last year, Thurmond used his carefully cultivated family to defuse two potentially explosive issues -- his age (74) and his outspokenly segregationist record.

The mere fact that Thurmond had a family consisting of his young wife Nancy, a former Miss South Carolina, and four children, aged 2 to 7, each campaigning clad in T-shirts that read, "Vote for My Daddy," was enough to defuse the age issue and convince voters that Thurmond was a geriatric miracle.

Thurmond's racist background posed an even trickier problem. In 1948 he had run as a segregationist candidate for president and as recently as 1965 had charged that the civil rights movement was "communist-led and-inspired." Beginning in 1970, when he hired his first black staff member, Thurmond began to bend with the times, funneling aid to black colleges and universities and becoming a last-minute advocate of voting rights for the District of Columbia.

But all this was window dressing compared to Thurmond's master stroke. Thurmond, who once said, "There are not enough laws on the books of the nation, nor can there be enough laws, to break down segregation in the South," enrolled his oldest daughter, Nancy Moore, in an elementary school in Columbia, S.C., that was 50 percent black. The wonderful thing about Thurmond's gesture was that after winning reelection, with a sizable fraction of the black vote, he moved his family back to the Washington area where Nancy Moore is happily enrolled in the posh and very private Potomac School.