WASHINGTON — Supreme Court justices said yesterday that New York’s system of letting political bosses essentially pick trial judges does not appear to violate the Constitution.

The Court heard arguments in a case brought by unsuccessful candidates for judgeships and a watchdog group. Among the plaintiffs is a judge who said she could not get the backing of local Democratic party leaders to move up to the state’s top trial court because she refused to hire their choices to be her aides.

The unique system has primary voters elect delegates to a convention that then chooses candidates who most often run unopposed in the general election.

Two federal courts had struck down the system, saying judgeship candidates who lack support from the party leaders are excluded from elections by an onerous process that violates their First Amendment rights.

Critics have said the conventions are patronage-driven affairs in which allies of party leaders are rewarded with judgeships and all others shut out.

The 2nd U.S. Circuit Court of Appeals said that between 1990 and 2002 almost half the state’s elections for Supreme Court justices — trial judges in New York’s judiciary — were uncontested, calling them “little more than ceremony.”

The appeals court ordered the state to dispense with the conventions and switch to primary elections until state lawmakers come up with a new plan. Many legal and civic groups have come out in favor of appointing judges in New York.

The justices did not appear bothered by the lack of competition or voter participation in the arcane nominating system.

“It’s a basic judgment not to have judges popularly elected,” conservative Justice Antonin Scalia said.

Justice David Souter, a liberal, said he did not see a constitutional problem in the ability of party bosses effectively to exclude some candidates. “For political reasons, they’re saying, ‘We don’t like you,’” Souter said.

The Court previously has ruled that states can decide whether to use conventions or primaries to nominate candidates. States also can choose to have judges appointed rather than elected.

“Well, doesn’t that seem kind of odd, that if a state can have no role for voters, it can have a pure convention, that they’re penalized if they have some role for voters?” Chief Justice John Roberts said.

Margarita Lopez Torres became the lead plaintiff in the lawsuit after Democratic leaders in Brooklyn blocked her from getting the party’s nomination for a Supreme Court judgeship. She said the leaders turned against her shortly after her election as a civil court judge when she would not hire people they recommended. Three years later, Lopez Torres said they offered her a second chance if she would hire a leader’s daughter. She refused.

The state, the Democratic and Republican parties and the elections board joined to ask the high court to reverse the appeals court ruling. Former New York Mayor Ed Koch was among a diverse group of politicians and legal groups asking the Court to uphold the lower court rulings.

The state Legislature adopted the nominating conventions 86 years ago. Lawmakers scrapped direct primaries for New York’s Supreme Court justices because of the potentially corrupting influence of having prospective judges raising campaign money. Other judges in New York are elected through primaries.

The plaintiffs have said the current system leads to cozy relationships among judges, lawyers and politicians.

A decision is expected by June.

The case is New York Board of Elections v. Torres, 06-766.