President Reagan?Ûªs top economic advisers yesterday abandoned the traditional Republican stance that government deficits are the main cause of inflation, warning that it would be a ?ÛÏdisaster?Û? if any basic change were made in the president?Ûªs economic policy.</br></br>William A. Niskanen, a member of the Council of Economic Advisers, stunned a conference sponsored by the American Enterprise Institute by arguing that ?ÛÏin general, concern about the [federal] deficit has been misplaced.</br></br>This new administration pitch was received by the AEI?Ûªs conservative establishment with only a slightly camouflaged sense of shock.</br></br>Herbert Stein, President Nixon?Ûªs chief economic adviser and chairman of yesterday?Ûªs session, retorted: ?ÛÏIt seems to me that President Reagan is the only member of the administration who believes that deficits are inflationary.?Û? administration is being buffeted by controversy over leaked budget es-?Û÷ timates showing $100 billion-plus deficits annually for the next three years.</br></br>Calling for ?ÛÏa new perspective?Û? on the budget, Niskanen suggested that instead of a goal of a balanced budget, the nation ?ÛÏshould be prepared to accept a deficit of $60 billion-plus ... for the current policy horizon?Û? to prevent a contraction in ?ÛÏthe net worth of the federal government.?Û?