Somewhere north of Washington, at the approximate confluence of the Beltway and the Baltimore-Washington Parkway, the Secret Service intends to build facades of both the White House and Blair House with a replica of Lafayette Park nearby. Maybe they will have replicas of pigeons and bag ladies also, but if it is realism they're after, they had better build a replica of the Oval Office. After all, the Secret Service has done more than protect the president's life. It has bugged his office, too.

The Secret Service, in fact, is the agency that three presidents have turned to when they wanted something done that was just possibly legal but certainly sleazy and unethical. It was the Secret Service, for example, that complied when John Kennedy said he wanted his phone calls recorded. It installed the tap that allowed the president to record phone calls from his aides, his allies, his friends and even his wife, none of whom, as far as we know, were threats to his life. Did the Secret Service think that Jackie, for instance, was going to throttle her husband with a Dior gown?

It was the Secret Service also that provided Richard Nixon with the rope with which he hanged himself. Its technicians installed the infamous taping system in both the White House and the Executive Office Building.

Once again they were the president's little minions, doing what he wanted even though what he wanted was unethical and had nothing at all to do with protecting his life. Like Ado Annie in the play "Oklahoma!", this is the agency that can't say no.

(It is worth noting that "Deep Throat," the all but legendary newspaper source, may not have been a high Nixon administration official after all, but a member of the Secret Service. Someone, after all, had to change the tape reels and check to see if the system was functioning. The only way to check is to listen.)

The Secret Service, though, did not limit itself to just bugging offices and tapping phones. No sireee. According to former presidential aide John Ehrlichman, when Richard Nixon worried that his brother, Don, might be involved in some politically embarrassing business deals, the president called in the Secret Service: "Beginning May 27 and until July 8, 1969, Secret Service agents trailed Don Nixon around Southern California and to New York, New Orleans and Las Vegas," Ehrlichman writes in his book, "Witness to Power." "Every three or four days, I received a written report of where Don went . . . "

But the Secret Service, Ehrlichman reports, felt it could not do its job well unless it tapped Donald Nixon's home and business telephone. This his brother, the president, authorized and this the Secret Service did although Don Nixon was hardly a threat to the president's life. Ehrlichman says the Secret Service had some experience in brother watching. Sam Houston Johnson had received the same courtesy from his brother, Lyndon.

None of these activities has anything at all to do with protecting the life--as opposed to the image--of the president. The agency now says it will not comment on the Donald Nixon affair and has no guideline forbidding it from bugging yet another presidential office--if it is asked. It has a very protective view of the presidency: If anyone is going to do the bugging, it's going to be them. The Secret Service will not, of course, break the law, but then it tends to think the president is the law.

The Secret Service, in fact, has used the national anxiety over political assassinations to hold itself above criticism. It bugs, it taps and it shields the president (or a candidate) from the press or sometimes from his own staff for any reason, sometimes so that mortal sins in high heels can be trotted up the back stairs. Almost never is it called to account for its actions and never has it been investigated by Congress for its habit of heel-clicking to presidential requests. It seems that standing between the president and a potential assassin means never having to say you're sorry.

The trouble with the Secret Service is that it has sworn its allegiance to the president and not just to the republic for which he stands. It doesn't need a facade of the White House. It needs a visit to the National Archives. That's where the Bill of Rights is kept.