MILLICENT FENWICK is, she says, "waiting for a sign."

Almost anything would do to push her into a race for the Senate seat on which Harrison Williams is precariously perched.

"I went to my doctor," she says, "thinking he could put an end to all this. But he says I can do anything I want for the next 20 years -- which was no help at all."

Ms. Fenwick is 7l years old and she wears a pacemaker.

By ordinary standards, a heart patient in her golden years would not seem the ideal candidate for a gruelling state-wide contest in a crowded field.

But she is not ordinary, and neither is her state.

New Jersey, its boosters protest, has no more political scandals than any other state, but they concede that it seems that way. Secretary of Labor Raymond Donovan says that merely to be from his home state is an indictable offense.

Currently each party is, or should be, hanging its head.

The Democrats have the case of Sen. Williams, who was convicted of taking bribes in the Abscam case, and who is fighting expulsion from the Senate.

The Republicans have just been caught at outrageous electoral skullduggery, reminiscent of Richard Nixon's dirtiest tricks.

Armed representatives of the GOP's National Ballot Security Task Force, wearing black armbands and carrying huge "Warning" signs went into central city wards with high black registration for the announced purpose of "protecting challenged voters" -- some of whom they succeeded in scaring away from the polls.

Republican National Committee chairman Richard Richards went on the offensive about the offense. Without the "ballot security" forces, he said, "The Democrats would have stolen the election."

Fenwick's reaction to the episode in no way reflected the official line: "That was a damn fool thing to do," she fumed.

It's that predilection for speaking her mind that makes her special in her party -- and also in the House, where she is the undisputed grande dame.

That and a couple of other things: Her elegant appearance -- she was once a Vogue model and is still a clotheshorse; her corncob pipe, her real pearls, her outspokeness -- she called her colleagues "pickpockets" for accepting a backdoor pay raise; her wealth -- she is worth $5 million.

In her five years in the House, she effortlessly became what the others in the pack long to be, a celebrity. She has been on "60 Minutes." She is a character in Doonesbury, where she is known as "Lacey Davenport" -- a genteel, charming aristocrat -- who is stricken over political corruption, environmental abuse and human rights violations.

Many have forgiven her her fame and her wealth, among them Democrats who envy her independence from the grubby political considerations they have to make.

Rep. Barbara Mikulski, the small, combative liberal Democrat from blue-collar Baltimore, who disagrees with her on many matters, unhesitatingly pronounces Fenwick "gutsy and honest."

Rep. Michael Barnes (D-Md.) says, "I hate to say it because she's in the wrong party, but I think she would be a dynamite candidate."

Some call her a "fraud" -- because she yearns over the poor and votes for Reagan's harsh economies -- and a "fake" -- because she inveighs against congressional pay raises when she obviously doesn't need the money. And she speaks too much, too soon for some of her colleagues. Andy Maguire, a former Democratic congressman who is getting into the race, says she would not wear well because of her "flakiness."

Polls taken in the governor's race picked up the fact that she leads Jeffrey Bell, a conservative Republican who has already announced his candidacy, by 20 points in statewide approval ratings.

The White House insists that the president, although Bell once worked for him and is closer ideologically, would be neutral -- just as he will be in California, where his daughter is running.

Fenwick agrees with Reagan on spending cuts, but differs on foreign policy and social issues and isn't so sure about White House good will. Independent efforts to make her human rights director at State or ambassador to Italy -- Italian is one of the three foreign languages she speaks fluently -- came to naught.

While she is waiting for the sign, Fenwick agonizes, ironically, over money. A vociferous defender of campaign reform, she has vowed never to accept PAC funds, because, she says, "How is the public to know if a congressman votes the PAC way because he believes it or because he was bought?"

She could use her own money but it will take at least $700,000 for the primary, and she frets over her obligations to her 11 grandchildren.

She admits to ambition.

"Yes, it's there," she said the other day. "I think it would be rather grand to be in the Senate."

New Jersey could use a little image burnishing right now. If they want a high-minded, pipe-smoking, opinionated lady, with beautiful cheekbones and unlimited candor to do the job, it's obvious she wants to apply.