The best thing that can be said for this assassination-plot plodder is that Britisher Archer (far more comfortable on home ground, Not a Penny More. . . . , 1976) leaves his would-be grabber-gimmick--it's 1983 and Ted Kennedy is President--tactfully unexplored. In fact, the focus isn't on bland Teddy and bland Joan at all, but on CIA Special Agent Marc Andrews, who's assigned to figure out which Mafia-supported Senator was overheard--by persons now very dead--plotting a March 10 shooting of the President (a slight disagreement over Ted's tough Gun-Control Bill). The suspects include, temporarily, Birch Bayh and Robert Byrd, a situation that offers some cutesy interest, but not nearly enough to sustain us through a sub-standard countdown and an all-too-standard romance-between Marc and the doctor-daughter of a Senator-suspect. She calls him ""G-man."" He calls her ""lovely lady."" We call them--and this--the pits.