SACRAMENTO, Calif. -- News that a sitting California senator is being investigated for sexual harassment against a young female employee has put a fresh spotlight on a legislative leader this week as he begins a bid against the state's first female U.S. senator.

Senate President Pro Tem Kevin de Leon, the Democratic leader of the state Senate, heads the committee in charge of human resources employees who handle workplace complaints. De Leon also rents a room in the Sacramento home of Democratic Sen. Tony Mendoza, the man accused of improper conduct, de Leon spokesman Anthony Reyes said.

Mendoza is accused of repeatedly inviting a young woman who worked in his office through a fellowship program to the house, although she never went. Mendoza said in a statement that he would never knowingly abuse his authority, though his statement didn't address the allegation that he invited her to his home.

De Leon said through spokesmen that he did not know about the complaint against Mendoza or his alleged invitations to the young woman. De Leon's allies have downplayed the two senators' relationship.

But De Leon's handling of impropriety at the Capitol will likely play a role in his U.S. Senate bid against Sen. Dianne Feinstein, one of California's most prominent women in politics and a powerful U.S. senator.

"It really does feel like we're at this inflection point with sex harassment allegations where suddenly they're being taken seriously," said Kim Nalder, director of the Project for an Informed Electorate at California State University-Sacramento. "It's hard to imagine that Kevin de Leon's bid will be completely untarnished by this revelation that someone close to him was accused of this kind of misbehavior."

The latest allegations against Mendoza, which come after nearly 150 women signed a letter three weeks ago calling harassment pervasive in the capital culture, shed further light on the Senate's murky processes for investigating its own members.

After the initial outcry about harassment in mid-October, De Leon and Assembly Speaker Anthony Rendon immediately pledged to review the Legislature's policies. De Leon hired an outside investigator, and the Senate asked women to speak to her.

De Leon said at the time that "everyone deserves a workplace free of fear, harassment and sexual misbehavior."

That statement was made before the allegations about Mendoza became public. A month earlier, the Senate began investigating Mendoza, Senate Secretary Danny Alvarez confirmed.

A former employee of Mendoza's complained to the Senate Rules Committee in September that the senator had repeatedly behaved inappropriately toward a young woman who worked for him through the Sacramento State fellows program, said Micha Liberty, a lawyer for the employee. That month, the employee and two others in Mendoza's office were fired. The Senate and Liberty dispute the timing of the firings relative to the complaint.

Mendoza and Alvarez said the firings had nothing to do with the complaints. Liberty, though, said her client made clear she was accusing Mendoza of sexual harassment toward the fellow, and she was forced to sign a confidentiality agreement when she was fired. Liberty would not name her client and did not provide a copy of the confidentiality letter.

Mendoza said he did not know about the complaint until the he was contacted by the Sacramento Bee. A spokesman for the university, Brian Blomster, said the university did not know either.

The Senate's policy says the deputy secretary for human resources will meet with people named in complaints or those who may have knowledge, and will attempt to treat investigations as confidential. Alvarez did not directly answer a question about when, if ever, de Leon would be notified about an investigation in his role as head of the Senate Rules Committee.

"As the process requires, the Senate will take action once Senate Rules completes their investigation," he said.

De Leon's spokespeople declined to make him available for an interview with The Associated Press on allegations of Capitol harassment despite repeated requests, including on Friday. They did not answer Friday when asked if de Leon had spoken to Mendoza since news of the allegations against him broke or if he planned to strip Mendoza of his committee chairmanship. Mendoza heads the Senate Banking, Insurance and Financial Institutions Committee and sits on other key committees.

De Leon campaign spokesman Roger Salazar pointed to his work on gender equity and fighting campus sexual assault as evidence of his record on women's issues. "We're not going to be able to stop people from being shameless in trying to play politics with this issue," Salazar said.

Feinstein's allies, though, said the allegations at the Capitol will hurt de Leon.

"De Leon is challenging a feminist icon," said Nathan Ballard, a Democratic strategist backing Feinstein. "There is now a dark cloud of impropriety surrounding de Leon that won't make him very popular with Sen. Feinstein's base of Democratic women."

It's hard to discern the full scope of sexual harassment allegations at the Capitol because lawmakers shield investigations from disclosure. The Senate and Assembly both rejected requests for information from the AP about how many sexual harassment investigations resulted in discipline since 2012, citing privacy concerns. The Senate reported that in that time it has investigated at least six sexual harassment complaints, although it's unclear if that tally includes Mendoza.

When complaints are resolved, employees who make them may never get documentation spelling out the results. Instead, the Deputy Secretary for Human Resources "will orally report the findings and conclusions to the employee," according to the Senate harassment policy.