RONALD REAGAN has become a liability to the Tennessee Republicans who rode his coattails two years ago. Cissy Baker, the 26-year-old daughter of Senate Majority Leader Howard Baker. is seeking an east Tennessee congressional scat: she spent the first month of her campaign dodging offers of help from Washington, which of late had given Tennessee little more than its 11 percent unemployment rate. She finally appeared with the President in a national GOP commercial last week, but even then, she demurred from supporting the Administration's economic program. The TV ad was merely evidence of her ability to "open doors in Washington."

The Senate race provides a dramatic constrast to these pirouettes. Sen. James Sasser, a liberal Democrat, is being challenged by Rep. Robin Beard, a doctrinaire conservative whose views on social issues and national defense place him far right of even the Republican party. Earlier in the year. Beard's emphasis on abortion, school prayer, a balanced budget, and aid to communist countries seemed to be working. His assertions that Sasser had voted both ways at different times on several of these questions struck home in this Bible-belt state.

BUT BEARD's charges have backfired. An anti-Sasser commercial featuring the antics of a wind-up mouse called "Flippin Jimmy" designed to highlight the Senator's alleged woffling on the issues, raised doubts as to Beard's seriousness and drew threats of a lawsuit from Sasser. A subsequent advertisement featured an actor portraying Fidel Castro lighting a cigar with a $100 bill and saying. "Thanks, Senor Sasser," referring to the Democrat's vote for a bill to extend U.S. aid to international development banks. Later to draw attention to Sasser's vote against a Constitutional amendment banning abortion, the Beard campaign financed a tour of the state by a fundamentalist religious leader who called the Senator a "murderer."

Although Beard later apologized to Sasser for the incident, it raised more questions about the challenger's qualifications for the U.S. Senate. Worse, his charges turned out to be inaccurate and misleading, and even prominent Republican politicians and editorials turned against him. Sasser now mentions Beard's campaign excesses only to ridicule them. Sasser emphasizes economic issues, offering a five-point economic stimulation package.

The Volunteer State seems more interested in the economy than in foreign policy questions, and Beard's own campaign practices, including his sluggishness in disclosing federal campaign financing information, make his charges right hollow. The Republican says he expects today to bring him victory in "the biggest upset in the history of Tennessee politics." More likely, it will bring a massive repudiation of his New Right Negativism.