Putting aside their dull-but-good image, Montgomery County's ruling Democratic politicians traded new accusations yesterday. The internecine infighting leading to next Tuesday's election produced these actions:

* County Council member Rose Crenca called her challenger, former school board member Thomas S. Israel, a liar and asked that he be investigated for unfair campaign tactics.

* Former acting governor Blair Lee III broke with tradition and took sides in a primary fight, supporting the campaign of state Sen. Laurence Levitan, under attack by businessman-candidate Anthony Puca for alleged conflicts of interest.

* A rare public shouting match between incumbent council members, representing rival slates, accompanied escalating charges about a radio commercial produced for one of the slates.

The Merit Team accused the rival United Democrats of employing "desperation politics unworthy of Montgomery County" for criticizing the controversial radio spot.

That ad, for Councilman David L. Scull, leader of the Merit Team, features a quotation from Democratic Congressman Michael D. Barnes, followed by the phrase "vote for all seven" Merit candidates. The United Democrats and Barnes complained over the weekend that the ad leaves the impression that the congressman has endorsed the Merit Team. Barnes said he has not endorsed either slate, but agreed to say good things about all Democrats.

At a press conference yesterday, Joseph Gebhardt, the attorney managing the Merit Team campaign, called the United Democrats' complaint "a non-issue" and a "last-minute attack." Gebhardt added, "Our campaign must be like Caesar's wife, totally above suspicion."

Nevertheless, Scull went to the WTOP radio studio late yesterday and retaped the closing words of the ad, replacing his voice for the announcer's to make a distinction between the Barnes quote and the call to "vote for all seven."

The dispute over the advertisement prompted an exchange between Merit Team member Esther Gelman and council President Neal Potter, head of the United Democrats.

"If you had a complaint why didn't you come to us?" Gelman yelled angrily. "Why did you go to the press?"

Potter replied, "We thought we'd give you a taste of your own medicine."

Gelman shot back: "You're accusing us of headline hunting and here you are doing it!"

"Well, it's a taste of your own medicine!" Potter repeated.

In another name-calling exchange between rival slate members, the United Democrat's Crenca said the Merit Team's Israel "has made statements which were not only lies but which he knew, or should have known, were lies."

Crenca was responding to accusations by Israel, in letters to precinct officials, that in her four years on the council she failed to author any legislation that became law. Crenca produced a list of five bills and four zoning amendments she claims credit for.

Israel admitted yesterday that he overlooked one Crenca-sponsored law but he said he stood by his accusations.

Levitan, who chairs the state Senate's powerful Budget and Taxation committee, has come under attack from two contenders, Democrat Puca and Allan C. Levey, the state Republican chairman who is seeking the GOP nomination in the district. Both challengers have accused Levitan of allowing state aid to Montgomery County to decline during his committee tenure.

Puca has also accused Levitan of conflicts of interest involving clients of his law firm and of voting against ethics bills and condominum conversion protections for tenants.

Lee, endorsing Levitan, distributed an "information fact sheet" to reporters showing that state aid to Montgomery has increased. The former acting governor also said Puca and Levey had resorted to "distortions and outright falsehoods. . . . Their tactics are far removed from the normal give and take of political debate; they remind us more of 1950s style McCarthyism."

Levitan also picked up endorsements from Barnes, County Executive Charles W. Gilchrist, state Senate President James Clark, and Sen. Margaret C. Schweinhaut (D-Kensington).

Lee and Clark called Levitan the county's most important asset in the state Senate as the state grapples with new formulas for dividing up state aid.

Puca and Levey said Montgomery's share of state revenue has declined, even if actual dollar amounts increased. Puca also angrily repeated accusations that he is being harassed by Levitan staffers, finding his literature torn down, and now having his state income tax payments tampered with.

Despite all the mudslinging, Barnes said he believes the county's good government reputation is still intact. "It's unfortunate that some of these things demean the political process and lower the standards set by some of our long-time standard bearers," Barnes said.