With the deepening of controversy over Harris County District Attorney Chuck Rosenthal's e-mails, high-profile assistant Kelly Siegler is calling on him to resign as she campaigns for election to his job.

Rosenthal “has made a lot of serious mistakes. Everybody here knows that; everybody in my office knows that,” Siegler said at a Republican candidate forum Monday. “It's sad. It's tragic. And it's time for Chuck to resign.

“He's also my friend. He's not a bad man. He needs to go.”

Siegler, known nationally for catchy trial techniques, made the comment when asked what weaknesses she might have as a candidate. She said she is grappling with a misguided perception that she shares responsibility for his errors.

“But do you really think that Chuck Rosenthal is me?” she asked. “And if you could only know how many conversations I have had with him to try to get him to do things differently or to listen. The problem is, Chuck quit listening to all of us a long time ago.”

Siegler's husband, Dr. Sam Siegler, who has been Rosenthal's physician, e-mailed sexually explicit material to the district attorney's government e-mail address. Siegler has criticized that action.

Other e-mails stored on Rosenthal's county computer last year contained racist and sexist jokes and notices for his re-election campaign.

As a federal court witness last week, Rosenthal acknowledged having made erroneous statements in a sworn deposition about his deletion of office e-mails. U.S. District Judge Kenneth Hoyt indefinitely postponed proceedings about whether Rosenthal should be punished for deleting what appeared to be evidence requested in a federal lawsuit against the county - and the testimony created questions about whether Rosenthal had admitted to lying under oath.

Rosenthal's attorney in the contempt proceedings is being paid by the county, with the fees capped at $50,000. According to the contract between Harris County and the law firm Marshall & Lewis, the county pays Ronald Lewis $400 an hour and associate attorneys $225 an hour.

The county Commissioners Court approved the contract, in which Lewis also represents two of Rosenthal's administrators, on Dec. 18.

In January, after Rosenthal aborted his campaign and Siegler became a candidate along with three other GOP contenders, she said she had recommended that he allow an independent agency to review convictions in cases involving tainted evidence from the Houston police crime lab. Rosenthal decided to have the cases reviewed by his staff instead.

But Monday was the first time that Siegler, who did volunteer work for Rosenthal's 2000 and 2004 election campaigns and rose to chief of his special crimes bureau, took the stance that Rosenthal should quit now. His four-year term runs through this year.

“I can change what needs to be changed in that office and  can start tomorrow because I know everybody there,” Siegler, an assistant district attorney for 21 years, told the Memorial West Republican Women.

The other GOP contenders say the prosecutors' agency needs a housecleaning that can best be accomplished by an outsider.

Rosenthal was not available for comment.

Defense lawyer and former prosecutor Jim Leitner, another candidate for district attorney, already has said Rosenthal should step down. The other Republican contenders, former judge Pat Lykos and police Capt. Doug Perry, said they were neutral on the issue.

The Republican primary winner will face Democrat C.O. Bradford, a former Houston police chief, in the November general election. Bradford, who was prosecuted by Rosenthal's staff on perjury charges that a judge later dismissed, declined to comment Monday, continuing his studied silence about Rosenthal's troubles.

The Texas attorney general's staff is investigating at the request of county government to see whether Rosenthal should face a removal lawsuit because of the e-mail contents. The local Republican Party leadership also has said he should resign.

Gov. Rick Perry has authority to appoint a successor, pending the outcome of the November election, if Rosenthal were to step down.

Leitner criticized Siegler for telling the Houston Chronicle recently that a prosecutor would be “lame” if he or she does not try telling the jury something he knows a judge is likely to throw out as improper.

“When you say you can break the rules and you're lame if you don't break the rules to get the end result that you want  that's what Chuck's problem is,” Leitner said.

Siegler said a prosecutor's job is “to find out what the truth is, not to convict at all costs.”

When Siegler used a question in the forum to point out Lykos' lack of experience as a prosecutor, Lykos, who presided over a criminal court, remarked, “I reckon men can't be obstetricians then.”