Clarence Norman Jr., the former assemblyman from Brooklyn, will use his fourth trial on criminal charges to try to rehabilitate his reputation, while prosecutors will use it as a forum to intensify the scrutiny on the alleged sale of judgeships in Brooklyn.

Norman, who served 12 terms in the state assembly and was chairman of the Brooklyn Democratic Party, has already been convicted at two separate trials for soliciting illegal campaign contributions and stealing a campaign check.

But in state Supreme Court in Brooklyn, where Norman’s latest trial began yesterday, his lawyer suggested that Norman was a voting rights hero who represented the ideal of “enfranchisement.” The lawyer, Anthony Ricco, went so far as to compare Norman, who was the first black chairman of the Kings County Democratic Party, to Martin Luther King Jr.

The current trial will take the panel of jurors back to the campaign season of 2002, when there were several unfilled civil court judgeships in Brooklyn. The trial will scrutinize the relationship that existed between Norman and two judicial candidates to whom he extended his support, Karen Yellen and Marcia Sikowitz.

Prosecutors charge Norman with strong-arming both candidates, who ended up losing, into paying his favored campaign consultants and printers under the threat that he would withdraw the support of the county organization.

An assistant district attorney, Kevin Richardson, described Norman’s alleged actions: “Because I’m the king of Brooklyn, they are going to do things my way or the highway.” To the candidates, Mr. Richardson said, the threat of losing the county organization’s support was “as loud as a bomb.”

“It rang deafening on those two candidates,” Mr. Richardson said.

Prosecutors describe the Ms. Yellen, a family court judge today, and Ms. Sikowitz, now a housing court referee, as victims. Norman stands charged of grand larceny, extortion, and coercion.

What prosecutors describe as extortion, Norman’s lawyer, Anthony Ricco, described as an effort to commandeer what Norman saw to be the losing campaigns of both candidates.

Mr. Ricco said that Norman was concerned that both candidates were ignoring several districts in Brooklyn with a high concentration of black voters. Norman tried to persuade both candidates, who are white, to campaign in those neighborhoods, which ended up accounting for 44.7% of the voters in the 2002 election, Mr. Ricco said.

“This case is about the 42nd, 43rd, 55th, 56th, 57th, and 58th Assembly districts,” Mr. Ricco said. The strategies of Judges Yellen and Sikowitz, according to Mr. Ricco, were, “Don’t spend money in those districts, because they vote for blacks.”

Norman, Mr. Ricco said, “tried to inspire them beyond their own ignorance, ignorance of themselves, and ignorance of the Brooklyn community.” Much of the defense’s efforts seem poised to be spent second-guessing the campaign strategies of both Judges Sikowitz and Yellen.

Today a surrogate court judge, Margarita Lopez Torres, will testify. Judge Lopez Torres was the lead plaintiff in a voting rights lawsuit that alleged Norman prevented voters from playing a role in the selection of state judges.