SAN FRANCISCO — With the growing recognition that prosecutors hold the keys to a fairer criminal justice system, the term “progressive prosecutor” has almost become trendy. This is how Senator Kamala Harris of California, a likely presidential candidate and a former prosecutor, describes herself.

But she’s not.

Time after time, when progressives urged her to embrace criminal justice reforms as a district attorney and then the state’s attorney general, Ms. Harris opposed them or stayed silent. Most troubling, Ms. Harris fought tooth and nail to uphold wrongful convictions that had been secured through official misconduct that included evidence tampering, false testimony and the suppression of crucial information by prosecutors.

Consider her record as San Francisco’s district attorney from 2004 to 2011. Ms. Harris was criticized in 2010 for withholding information about a police laboratory technician who had been accused of “intentionally sabotaging” her work and stealing drugs from the lab. After a memo surfaced showing that Ms. Harris’s deputies knew about the technician’s wrongdoing and recent conviction, but failed to alert defense lawyers, a judge condemned Ms. Harris’s indifference to the systemic violation of the defendants’ constitutional rights.

Ms. Harris contested the ruling by arguing that the judge, whose husband was a defense attorney and had spoken publicly about the importance of disclosing evidence, had a conflict of interest. Ms. Harris lost. More than 600 cases handled by the corrupt technician were dismissed.