On election night last year, the liberal reformers joined hands and literally danced around Philadelphia's ornate old city hall singing, "Ding Dong the Witch is Dead."

Mayor Frank L. Rizzo was their witch. He was defeated on that day in his attempt to change the city charter to allow him to seek a third successive term. And he was beaten badly, by 2 to 1.

Now, the word from the "witch," better known as the "Cisco Kid," from his days as a swashbuckling policeman, is that the liberal munchkins had better beware. He is alive as ever and ready to seek a seat as U.S. senator from Pennsylvania. Or so he would have voters believe.

"I think my voice is needed in this country," Rizzo said recently in stating his interest in the Senate race. "A good many people have my philosophy, but they don't speak out."

The mayor's statement of intent is a long step from a formal candidacy for the seat now held by Republican Richard Schweiker. Even some of his closest advisers think Rizzo is just beating his chest until his term as mayor expires in January.

Among other things, they point out, the mayor does not like to fly -- a necessity for a statewide campaign.

"When he went to Italy [to attend the canonization ceremonies for St. John Neumann], we had to put him in a police car, turn all the sirens on, drive it into the plane and keep the blue lights flashing until it landed," joked one Rizzo aide.

Moreover, Rizzo has never been tested on a statewide basis. And Pennsylvania voters last year appeared to be attracted more to the low key efforts of Republican Gov. Richard Thornburgh than Rizzo's flamboyant brand of old-time religion.

Rizzo, in an interview, scoffed at such detractions. "I'm giving the Senate serious, serious consideration," he said. In the past he has dismissed the fear of flying as "just another myth about me." And he hinted in the interview that he even was developing something quite foreign to him -- a foreign policy.

"For one thing I think that we shouldn't be so nice to countries who aren't so friendly to us," Rizzo said.

As for his defeat last November? "We were trailing 4 to 1 when I started campaigning. I brought that down to 2 to 1. If the election were held today, I'd win."

Even critics of the mayor are not so certain that he couldn't do just that running against a flesh and blood candidate rather than in a referendum against a city charter provision.

Rizzo strikes nerves. He has a unique personal presence and charm surprising to those who meet him for the first time. His supporters call it charisma, detractors see it as the trick of a demagogue.

Most recently he came out swinging at the U.S. Justice Department and its suit against the ctiy and Ruzzo alleging an officially condoned policy of police abuse of citizens.

Rizzo called the suit "hogwash." Then, in a nationally televised program, he bellowed that the Justice Department was undermining the American way of life by ignoring the civil rights of a majority of law-abiding citizens intimidated by criminals.

(He also boasted that the Philadelphia police department was so strong it "could invade Cuba and win.")

As a result of that appearance he received more than 7,000 letters of approval and checks of up to $1,000 (quickly returned) in support of him and of the police.

At another point, in 1978, he announced that he would "lead a charge across this country" campaigning for equal treatment for whites. During the charter change campaign, he called on voters to "vote white," a slip he quickly modified.

Such is the timbre of Rizzo's platform. He accused "ultra liberals" and the news media of undermining respect for authority. Black "militants" -- the Rizzo definition includes Benjamin Hooks of the NAACP -- seek an unfair advantage in job hiring and college admissions. The answer to city problems is to build, build, build. (The city now has over $1 billion in private and public projects under way.)

Could that platform play in another big city like Pittsburgh? Could Rizzo win on a statewide basis with such an appeal?

"He has no chance," said Richard Chapman, former director of the Philadelphia chapter of Americans for Democratic Action (ADA) and a longtime foe of Rizzo.

"As early as 1976, Jimmy Carter found [in the primary] that Rizzo made a great whipping boy in the rest of the state," Chapman said.

The 1978 gubernatorial candidates, Thornburgh and Democrat Pete Flaherty, discovered the same thing last year. Both opposed the Rizzo backed charter change and found that position politically profitable.

Chapman conceded, however, that the race for the Senate nomination in both parties is up in the air. "I don't get the sense that anyone knows what the hell is going on," he said. "It's just wide open."

On the Democratic side, Flaherty is considered a probable candidate. State Sen. Craig Lewis of the Philadelphia area is the only formally announced candidate. Joseph Rhodes, a black Pittsburgh state legislator, is expected to announce as is John Pittinger, a former state secretary of education.

Former Nixon White House chief of staff Alexander Haig, who now lives in the Philadelphia suburbs, is considered a strong Republican candidate, if his presidential aspirations fade. A number of little-known Republican congressmen may seek the nomination. There is speculation that William Scranton III, Thornburgh's lieutenant governor, might also try for the Senate -- although thus far he has said he is not interested.

It would not be impossible for Rizzo to obtain the nomination in such a field, given his formidable abilities as a fund-raiser and his still strong base in the city.

Aside from the Senate, he is said now to be considering a lucrative job as a celebrity security director for an Atlantic City gambling casion -- a rumor on which he will not comment.

Simple retirement would be easy enough for Rizzo. At age 58, he can look forward to a pension of $44,000 a year.

But he is a restless figure when not a part of public controversy. And it is quite possible that Rizzo, who his biographers described as "the cop who would be king," seriously sees himself as the mayor who should be senator.