Democratic National Committee Chairman Paul G. Kirk Jr. yesterday predicted a comeback for his party in the 1986 and 1988 elections, arguing that the Republican party will be burdened by its policy failures, particularly the huge federal budget and trade deficits.

Democratic party's defeats since 1980 are due to President Reagan's personal popularity rather than a nationwide shift to the Republican party, and now "the actor is leaving the stage," Kirk told an audience at Harvard University's John F. Kennedy School of Government.

"Only 10 months into the second term of this administration, the post-Reagan era has begun," Kirk said. "Talk of realignment is being replaced by reality. Triumph is being replaced by trouble in the Republican ranks."

Republican candidates are being left to run on Reagan's record without his personality and popularity to help them, Kirk said. "The very senators who were swept into office on the coattails of personal popularity in 1980 can feel the tidal wave of Republican red ink sweeping them out of office in 1986 -- Steve Symms of Idaho, James Abdnor of South Dakota, Mark Andrews of North Dakota, Paula Hawkins of Florida, Charles Grassley of Iowa -- just to name several who are now running away from Ronald Reagan's policies," Kirk said.

"As Joe Louis used to say, 'They can run but they can't hide.' "

Kirk said that Republican senators seeking reelection in 1986 and potential 1988 presidential candidates are pursuing an independent course or repudiating the Reagan record. He said that record includes mounting budget deficits, trade imbalances, the farm crisis, the administration's policy condoning "repression and racism" in South Africa and the weapons "spending spree."

"Many pragmatic Republicans are coming to realize that the policies of their party have set this country on a collision course with the future and have jeopardized their own political future as well," Kirk said. "Small wonder that Republican candidates of 1986, struggling for their own political survival, are distancing themselves from the policies of their own party."

Kirk said the announced retirements of Republican Sens. Paul Laxalt of Nevada, the general chairman of the Republican Party; John P. East of North Carolina and Charles McC. Mathias Jr. of Maryland were decisions "that the Republican fight is not a fight worth making in 1986 [and] greatly improve the chances for a Democratic Party majority in the U.S. Senate next year." He also predicted that "the party that embraces [Sen. Jesse] Helms [R-N.C.] and [the Rev. Jerry] Falwell" of the Moral Majority will splinter on "the litmus tests of the radical right wing."