NONFICTION : UP ‘TIL NOW: A MEMOIR OF THE DECLINE OF AMERICAN POLITICS by Eugene McCarthy (Harcourt Brace Jovanovich: $16.95; 258 pp.).

The only candidate who can claim to have denied a sitting President the re-nomination of his own party (Lyndon Johnson), Eugene McCarthy is also the only ex-senator I know of who has authored more than a dozen books. You’d think he’d have mastered the knack by now.

Like its convoluted subtitle, “A Memoir of the Decline of American Politics,” “Up ‘Til Now” is two separate efforts jammed together into one package. The memoir is by far the lesser effort, with McCarthy painting acidic miniportraits of the “as I remember them” variety. His targets are mainly former congressional colleagues and the various men who have run for President since McCarthy entered Congress in 1949.

The memories are far from fond. With the single exception of Adlai Stevenson, there isn’t a presidential candidate of either party of whom he approves. And no slight is too slight to escape McCarthy’s notice. When John Kennedy crossed him on a labor bill amendment in 1959, McCarthy concluded that he “could never accept his more than casual word on a legislative matter.” When Johnson, as President, stepped out on the floor of the 1964 Democratic convention while McCarthy was giving a speech, it was noted.

America’s (declining) politics is handled less churlishly. McCarthy’s assertion that we have allowed ourselves to slip back into the status of a colony, unable to control our monetary system, foreign policy or even our own boarders is provocative. His example of our selling timber and iron ore to Japan and buying back fiberboard and autos is intriguing. But it’s all hurriedly written in a brief 51-page section, as if McCarthy had a lunch to which he was going to be late. Where McCarthy is concerned, practice very definitely doesn’t make perfect.