Four San Francisco public defenders decided over drinks to challenge four Superior Court judges in the June 5 election. Their themes are synced: the criminal justice system is broken, the judiciary does not reflect the diversity of the population it serves, the incumbent was appointed by a Republican governor, and a public defender’s perspective is needed on the bench.

In other words, each is trying to make this a political contest.

There are better ways — and better reasons — to become a judge.

While the four public defenders have every right to run, the ouster of an incumbent judge should be based on a record that shows dereliction of his or her duty to act with integrity, competence and fidelity to the law. None of the four challengers has made such a case against Judges Curtis Karnow, Cynthia Ming-mei Lee, Andrew Cheng and Jeffrey Ross.

Rather, the challengers’ arguments are based more on generalities about the state of the judiciary than specific, well-documented evidence of malfeasance or misapplication of the law by the incumbents they are challenging.

In separate interviews with our editorial board, each bristled at questions about whether this coordinated campaign represents a threat to the independence of the judiciary.

“This whole thing about judicial independence,” said Nicole Solis, challenging Ross, “it’s a fallacy.”

It is not. In recent years, conservatives have been targeting judges they regard as too liberal in states such as Florida, North Carolina, Montana, Michigan and Texas, to name a few. If the principle of putting an ideological hue on the judiciary is wrong in red states, it’s equally wrong in deep-blue San Francisco.

Judge Karnow is a particularly odd target for this ambush from the left. His 2008 article in the Berkeley Journal of Criminal Law, “Setting Bail for Public Safety,” is often cited by progressives who want to reform a bail system that discriminates against he poor. He has developed courses to help officers of the court identify and prevent implicit bias in the system. He is one of the few San Francisco judges equipped to take on complex cases about technology.

It is noteworthy that, for all their talk about aspiring for the judiciary, only one of the public defenders (Kwixuan Maloof, challenging Lee) bothered to apply for a gubernatorial appointment to the bench. Evangelista (opposing Karnow) said she considered it, but merely printed out an application. Solis said she knew she wanted to run “before we met for drinks” but had not sought an appointment. Asked if he would apply if he did not win in June, Streets (challenging Cheng) said, “I’ll just think about that when the time comes.”

There is no doubt about the depth of passion and courtroom experience of the four challengers. Each has an impressive life story of overcoming odds to achieve a law degree and prosper in the profession. They may well be contenders for an appointment after vetting from the State Bar’s Commission on Judicial Nominations Evaluation, which investigates the background and qualifications of would-be judges.

The incumbents passed that test on their paths to the bench, and have done their jobs sufficiently well to draw the support of the presiding judge (a Democratic appointee) and assistant presiding judge (a Republican appointee).

Voters have been given the authority to replace a judge who is abusing his or her discretion within the law. The burden is on a challenger to make that case. To otherwise turn a judicial election into a partisan showdown or ideological loyalties test is the definition of an assault on judicial independence. Regrettably, that is what is happening here.

San Franciscans should vote to retain Judges Karnow, Lee, Cheng and Ross.

This commentary is from The Chronicle’s editorial board. We invite you to express your views in a letter to the editor. Please submit your letter via our online form: SFChronicle.com/letters.

Talking points versus the facts

The four San Francisco public defenders who are challenging incumbent judges are employing talking points that are either misleading or flat-out inaccurate:

Talking point: They needed to run for office because the judiciary is not becoming diverse through the appointment process.

Fact: California’s judicial bench has become steadily more diverse in each of the past 12 years. In the past seven years under Gov. Jerry Brown, more than half of his 451 judicial appointments have been women, and nearly 40 percent have been nonwhite. In each case, that exceeds the demographic group’s proportion in the applicant pool.

Talking point: The incumbents were all appointed by Gov. Arnold Schwarzenegger, a Republican.

Fact: Actually, all four judges are registered Democrats. Also, Schwarzenegger was decidedly bipartisan in his judicial appointments: 285 Republicans, 234 Democrats, and 50 who declined to state a party preference.

Talking point: Public defenders have little chance of getting appointed.

Fact: That may have been true in the past, but not under the Brown administration. In fact, four of 17 San Francisco judges appointed by Brown have been public defenders.