Republican Bernard E. Epton today called integrity the "overriding" issue in the Chicago mayoral election and launched a $100,000-a-week media campaign bludgeoning Rep. Harold Washington (D-Ill.) as a former imprisoned felon unworthy of being the city's next mayor.

Windy City politics are traditionally robust, but some political observers here were somewhat disbelieving of the intensity of Epton's media effort in the final three weeks of a campaign already laced with racial overtones. Washington, victor in a bitter three-way primary, is bidding to become the first black mayor of this overwhelmingly Democratic city.

One typical TV commercial describes Epton as a "distinguished legislator, lawyer and businessman . . . honored repeatedly for service to his country and his community."

Washington, it notes, was "found guilty of converting clients' money to his own use . . . barred from practicing law for five years . . . convicted and jailed for repeated criminal tax law violations . . . didn't even file his returns for 19 years."

"Which one do you think should be Chicago's next mayor?" the announcer asks.

Another ad appeals more directly for Democratic votes by quoting John F. Kennedy as saying, "Sometimes party loyalty asks too much," and concluding, "Surely this is such a time."

The theme of the ads is "Epton for mayor, before it's too late."

"We think the city would be making a very serious mistake to choose a man with the kind of background that Harold Washington has," said political consultant John Deardourff, who produced the ads.

When asked why the ads, to be shown in a city that is 40 percent black, had no blacks in them, Deardourff said the campaign could not find any blacks willing to appear in commercials.

"I think the blacks in this city have decided that they are going to vote for a black candidate," Deardourff said. Asked if that meant he felt blacks had written off Epton, Deardourff responded, "Yes."

Patrick Caddell, Deardourff's counterpart in Washington's campaign, criticized the Epton ads.

"I think most rational people judging politics would say it's a racist appeal. I certainly would," Caddell said.

The unveiling of the media campaign was one of several major events in the campaign today, following Monday night's lively and barb-filled hour-long televised debate between Washington and Epton.

Incumbent Mayor Jane M. Byrne, who lost in the primary, endorsed Washington afterward and then announced last week that she would be a write-in candidate in the April 12 general election, did not participate in the debate, which was sponsored by The Chicago Sun-Times.

But Byrne called a news conference at City Hall today and berated both candidates' performances as comic relief.

"It was like a nightclub act. It was very humorous, but it doesn't save the city," Byrne said. "I obviously feel it's exactly what caused me to get in the race. We've seen enough personality and charges and countercharges, but when are they going to talk about running a city?"

Byrne was vague today on her campaign, declining to say how much money it had raised, refusing to name the six committeemen she says are supporting her, saying she never was turned down by top officials in her primary campaign who are not among those listed as heading the write-in effort. She said she didn't ask them because she figured they probably would say no.

Even two members of the new team withdrew today, leaving some wondering whether Byrne's campaign would ever get going. The two men, Thomas E. King and James W. Bidwell, are executives of the Merchandise Mart, which is owned by the Kennedy family.

Sen. Edward M. Kennedy's (D-Mass.) office called to inquire about their roles in the campaign, and the two men announced that they would not be with Byrne after all. Bidwell termed the announcement of his role a mistake.

Kennedy endorsed Byrne in the primary, but is expected here Wednesday to urge all Democrats to unite behind Washington, who so far has had major difficulties garnering support from party regulars--the targets of his maverick campaign in the primary.

Byrne began formal efforts today to alleviate some of the technical problems confronting her write-in campaign. Her lawyers asked the city's elections board to print ballots that would have "mayor" and a space to write in her name. Otherwise voters would have to write in the title, her name, draw a box and check it for their votes to count. A ruling on that request is expected Wednesday.