In his rebuttal of a Post story assigning him status as a "senator elected by the New Right" ("South Dakota, By the Way, Has No Harbors," Free for All, Jan. 23), Sen. James Abdnor (R-S.D.) seems to have an overly selective memory of his 1980 campaign.

He would have us believe that his reasons for running were based on "widely different philosophies" with the incumbent senator, George McGovern, and that the National Conservative Political Action Committee was only briefly involved in the South Dakota Senate race.

The fact is that NCPAC was involved well before Abdnor decided to run. The NCPAC negative direct mail campaign started in January 1979. There is compelling evidence that Abdnor decided to get into the race only after NCPAC became dissatisfied with the array of Republican candidates and convinced Abdnor to make the race.

I don't think that even Abdnor will deny that he met several times with NCPAC representatives before making his announcement for the Senate. Even Abdnor's Federal Elections Commission reports show a contribution in kind of a NCPAC poll to which Abdnor had access.

He also suggests that he ran a "dignified campaign." It is easy to do so when your sleazy partners are spending well in excess of half a million dollars in a heavy- handed negative attack against the incumbent. As John T. Dolan, executive director of NCPAC, has said, "An organization like ours can lie through its teeth and the candidate we help stays clean." And, as Abdnor said in the summer of 1980, "I have no quarrel with NCPAC. They have a lot of great guys in it."

In May 1980, the McGovern campaign was instrumental in filing a suit against NCPAC with the FEC, alleging close "cooperation, consultation and coordination" between NCPAC and the Abdnor campaign. The action was dismissed. NCPAC's Dolan later commented, "Common sense tells you McGovern was correct," and "I know we did it, we admit it. He (Abdnor) admits it. We just led him up to the nomination."

Only when there was a hint of a backlash against Abdnor and NCPAC did he file suit against them with the FEC. But NCPAC, as late as October 1980, continued to send direct mail letters in Abdnor's behalf with a disclaimer indicating that the letter was authorized by the Abdnor campaign committee.

If Abdnor is not a "New Right Senator" then there are no current members of the Senate who can be so labeled.

With all the problems faced by South Dakota and the country in the Reagan era, one would hope that Abdnor would tend to his Senate responsibilities and stop trying to rewrite political history. Me thinks he do protest too much.