Brooklyn District Attorney Charles Hynes won his biggest victory to date today against the former chairman of the borough’s Democratic party. After nearly three days of deliberations, a Brooklyn jury found Clarence Norman Jr. guilty of extorting a judicial candidate.

Norman’s most recent trial — his fourth — was the first to address, even indirectly, allegations that judgeships have been bought and sold in Brooklyn. Mr. Hynes has staked his legacy on the outcome of his investigation into the sale of judgeships. The investigation, now in its fifth year, continues, Mr. Hynes’ deputy, Michael Vecchione, said following the verdict.

Prosecutors tried Norman, 55, on charges that he strong-armed two judicial candidates into paying his favored political consultants to campaign for them in central Brooklyn, an area in which neither candidate planned on campaigning heavily. Norman, formerly a 12-term assemblyman from Brooklyn, had threatened to withdraw his political machine’s support unless the candidates placed their campaign largely under his direction, prosecutors said.

Few judicial candidates consider themselves politicians, and the three-week-long trial opened a window on how deeply candidates believed they needed Norman’s support to win election.

One of the two candidates, Karen Yellen, testified she feared she would be “out of a job” if she failed to follow Norman’s directions. “I would no longer be a judge,” she said.

Ms. Yellen, an incumbent judge at the time, said Norman told her “we will dump you” unless she followed his instructions.

Prosecutors sought to portray Norman as “a thug” with the power to kill any judicial candidacy simply by refusing to give his support. In finding Norman guilty of grand larceny in the third degree by extortion, the jury appeared to endorse the prosecution’s view of Norman.

Norman’s criminal act, the jury found, was to demand that Ms. Yellen direct her campaign money to pay for mass mailings in Central Brooklyn and for $9,000 worth of campaign activities on election day. The $9,000 check went to a friend of Mr. Norman’s, William Boone III, who campaigned for the candidates, according to Mr. Boone’s testimony.

The jury today, however, acquitted Norman of all charges that he had also extorted a second candidate for the bench, Marcia Sikowitz.

At trial, Norman’s lawyers said the defendant’s actions were those of a frustrated politician facing two stubborn candidates in danger of losing their elections. Norman’s attorneys, Edward Wilford and Anthony Ricco, argued that the two candidates, both of whom were white, were dismissive of the thought of campaigning in the heavily black districts to which Mr. Norman sought to direct their efforts. His lawyers portrayed Norman as a voting-rights hero.

Mr. Wilford said yesterday that Norman was convicted of actions that occurred daily in politics.

“Mr. Norman wanted to win the election and he did what he though was best to win, including having to convince these candidates to spend money in the Central Brooklyn districts,” Mr. Wilford said. “He was convicted for asking the judges to pay their pro-rata share of expenses.”

Of Norman’s reaction, Mr. Wilford said: “Of course he’s disappointed that he’s not completely vindicated but he’s pleased that the jury said not guilty and that he’s still walking the streets of New York.”

In addition to the felony charge, the jury convicted Norman on misdemeanor counts of attempted grand larceny and coercion.

Today’s verdict brings Norman, who remains free, one step closer to prison. On Monday he will appear before Judge Martin Marcus to post $50,000 bail.

In his first three trials, Norman was acquitted of seeking improper reimbursement from the state for driving mileage, but was convicted of two campaign-finance violations. Those convictions are under appeal.

The trial just concluded will not be the last time a panel will be asked to consider Norman’s role in judicial selection in Brooklyn. The Supreme Court recently agreed to hear a case alleging that Norman’s Democratic machine had such a tight grip on the nomination process for state judges that candidates were denied their constitutional right to seek office.