Two weeks after Mayor Anthony A. Williams opened his second term by vowing the highest ethical standards for his administration, he is yet again trying to fight off a scandal that has engulfed several close associates and threatens others.

None of the allegations involving his connection to the Washington Teachers' Union, which is under federal investigation over missing funds, point to misbehavior by the mayor himself.

But, as in earlier lapses, his choices of allies and underlings have come into question, city officials and political observers say. They add that the sheer repetition of scandals -- three in the past 12 months -- could erode the mayor's reputation as a high-minded, though not gregarious, technocrat.

Williams yesterday sought to distance himself from the union officials who are under investigation, including the former co-chairman of his reelection campaign. "I have not, do not run the teachers union," he said.

Yet he announced that his administration would investigate a Washington Post report that union officials sought to steer city jobs to friends and family members and a contract to an associate. The mayor also acknowledged a history of making poor judgments.

"I've made a number of beauts in terms of stupid decisions. I've already said that over and over again," Williams said. "I apologize for those mistakes. . . . What people want to see is, they want to see results. They want to see me govern this city and move this city forward. And that's what I'm determined to do."

Questions about the mayor and the teachers union have grown into a major distraction for an administration that had just begun to embark on initiatives, announced in the mayor's inaugural address, to raise the city's literacy rate, improve public schools and attract 100,000 new residents.

The frequency of scandal is prompting concern even from the mayor's traditionally solid supporters in the business community, which has embraced Williams as an antidote to the troubled final years of Marion Barry's tenure.

Robert A. Peck, president of the Greater Washington Board of Trade and a former Williams appointee to the city's school board, said, "We're looking for some signs that the shortcomings that became all too apparent during the campaign are going to be addressed."

Yesterday's expression of contrition by the mayor, and his promise to get to the bottom of allegations, had a familiar ring to many in the city's political community.

The mayor made similar comments in March, after the city's inspector general reported improper fundraising by several administration officials, including his former chief of staff, Abdusalam Omer, and a second top aide, Mark Jones. Both departed city government under a cloud.

Then, throughout the summer, after civic activists discovered thousands of fraudulent and forged signatures on the mayor's nominating petitions, Williams repeatedly portrayed himself as a lax manager victimized by the failings of subordinates. A campaign aide, Scott Bishop Sr., was put on indefinite leave, and the campaign's top consultant, Charles N. Duncan, resigned.

There have been other unplanned departures under Williams, including Fire Chief Ronnie Few and Parks and Recreation Director Robert P. Newman, both of whom inflated their re{acute}sume{acute}s.

And there has been a series of rebukes by city election officials, who found that Williams failed to disclose income from city contractors when he ran for office in 1998 and improperly used city government resources to push a ballot initiative in 2000. Last year's fine for the fraudulent nominating petitions set a record, at $277,700.

The D.C. Board of Elections and Ethics opened a new investigation this week into whether work provided by teachers union officials and phone banks furnished by the union amounted to improper and undisclosed contributions to the Williams campaign.

"The public confidence must be diminished and his moral authority must be diminished, because there have been so many scandals involving his administration," said former D.C. Council member Bill Lightfoot. "They consistently demonstrate a lack of knowledge of the law."

Williams tacitly acknowledged past troubles and declared a new era in his Jan. 2 inaugural speech, saying: "I have put in place the highest standards for ethics and performance, because that is what it takes to maintain the public trust, your trust. You can count on me for that."

The latest trouble surrounds the mayor's former campaign co-chairman, Gwendolyn M. Hemphill, one of three teachers union officials accused in a federal affidavit of misusing $2 million in union funds. Hemphill allegedly bought a $13,000 television with union funds, and her husband, a Williams Cabinet member whose departure was announced last week, paid for the installation of the television. No charges have been filed.

Hemphill, who resigned from the campaign in October, is a former Barry labor official who nimbly acquired even more power and prominence when Williams became mayor. The teachers union broke with most of the city's labor community in 1998 to back Williams, and Hemphill and Barbara A. Bullock, then the union's president, lobbied the new administration hard for hires and appointments to boards and commissions, former officials have said.

"I am still amazed at the fact that he seems to have such poor judgment in people he hires," said D.C. Council member Sharon Ambrose (D-Ward 6), a frequent critic of Williams. "What you do see, more and more, is this reworking of Marion Barry folks."

Hemphill this week alleged that the mayor's chief of staff, Kelvin J. Robinson, asked her to pay a $2,000 bill for T-shirts purchased for the Democratic National Convention in 2000. She used teachers union money to pay the bill and said that is what Robinson expected; Robinson says he expected Hemphill to pay the bill from campaign funds.

In a separate allegation, another former Williams administration official, Charles F. Holman III, has alleged that while he was head of the Office of Human Rights, Bullock demanded that he give a contract to a lawyer affiliated with the union. Holman, who was fired after complaints were made by subordinates, said that acting chief of staff Joy Arnold arranged to steer that contract to the lawyer.

Williams said yesterday that although the teachers union sought to exert influence, it was not to an inappropriate degree, and many of its requests were rejected. Even so, he promised to investigate that allegation.

Administration officials express confidence that the scandal will blow over soon, revealing little more than the mayor's unwise choice in a campaign co-chairman.

"I look at this as going through a debris field of something, of explosions, that happened in the past, and now we're going through the consequences," he said. "But people elected me knowing that there were issues, knowing that I've had problems, knowing that I've made mistakes."