Just when you thought the GOP campaign in Michigan could not sink any lower, two of Pat Robertson's Michigan campaign aides admitted making an illegal mass mailing of an editorial by New Hampshire Union Leader publisher Nackey Loeb that said Vice President Bush should have his mouth washed out for using an obscenity.

Two of Bush's Michigan cochairmen demanded that Robertson fire the staffers and apologize to the Bush campaign for "this immoral and illegal act."

"They are throwing rocks," exclaimed David Walters, Robertson's regional political director. "It's ridiculous. Give us a break."

Walters said reprints of the Loeb editorial were mailed by the Robertson campaign to more than 9,000 precinct delegates just before last week's county and district conventions. The mailing did not identify who sent or financed it as required by federal regulations aimed at letting voters know who is attacking whom. It was a mistake made by campaign volunteers, Walters said.

But Peter Secchia, a Michigan Republican national committeeman and a Bush cochairman, said, "I charge it was deliberately done to hide the source of the expenditure." Oakland County Prosecutor L. Brooks Patterson, another Bush cochairman, filed a complaint with the State Elections Office and said he is sending another to the Federal Election Commission.

In the Nov. 10, 1987, editorial, Loeb accused Bush of responding with an expletive when a Florida Republican asked him in 1980 about the abortion issue and again in rejecting an invitation to a Conservative PAC '87 meeting.