Prosecutors announced Wednesday that no charges would be filed in the case of a New Jersey state official who alleged that she was sexually assaulted by another staffer working to elect Democratic Gov. Phil Murphy in 2017, then claimed Murphy left her in the lurch when she tried to bring the matter to his attention.

New Jersey prosecutors said there was "a lack of credible evidence" to move forward with a case.

Katie Brennan, the chief of staff of the state's housing finance agency, accused Albert Alvarez of raping her on April 8, 2017, after Alvarez drove her home from a campaign event while they were both working to get Murphy elected. Alvarez, who left as the chief of staff of the Schools Development Authority in October when a news account of the accusation was about to come out, has denied the allegation through his attorney.

"Due to a lack of credible evidence and corroboration that a crime was committed, the Middlesex County Prosecutor's Office will not be filing any criminal charges in this matter," the office said in a statement.

Brennan's attorney said she was disappointed with the decision.

In June 2018, The Wall Street Journal reported, Brennan emailed Murphy and his wife, asking to speak with them about a "sensitive matter" that had occurred the previous year.

Although Brennan did not specify the nature of the matter, Murphy responded within an hour and said he would schedule a meeting to talk with Brennan, The Journal reported.

“Hang in,” Murphy wrote to Brennan. “We are on it.”

But the meeting never happened, and there were no ramifications for Alvarez, the paper reported.

In October, both of New Jersey's legislative houses voted to start a special commission to look into why Alvarez then scored a $140,000-per-year job in Murphy's administration.

Brennan is suing the state over its handling of her allegation, which she reported to law enforcement after the alleged April 2017 assault as well as to officials in the governor's transition and administration. She has said the administration botched its response to her claims, which officials have testified that they found to be credible.

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Murphy has defended his administration's handling of the allegations, which included his chief counsel alerting the office's ethics adviser. But he also has said he wishes Alvarez was never hired to work in the administration after the campaign. Who hired Alvarez is not clear.

"You look at this woman's story, and it makes you sick -- the lack of the structure in our society, the lack of respect for survivors," Murphy said at a news conference last year. "So, my goals are to figure out what happened, let's get our government policies the very best they can be, let's make New Jersey broadly ... a society that people look up to and say, 'They respect survivors unlike anybody else.' Let's keep politics out of it."

Murphy's chief of staff and chief counsel asked Alvarez to leave in March and June, but they stopped short of firing him. He left when it was clear that The Wall Street Journal was about to publish an account of Brennan's accusations in October.

The Middlesex prosecutor has not detailed what it did in its review, but the office said it conducted an independent review of criminal allegations and declined to bring charges.

"We are deeply disturbed and disappointed by this egregious miscarriage of justice," Brennan's attorney, Katy McClure, said in a statement.

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Murphy has also hired former state Supreme Court Justice Peter Verniero to review his administration's handling of the case. Murphy said Wednesday he did not know when Verniero's review would be done.

"I would hope it's imminent," he said at an unrelated event earlier Wednesday.

Instances of alleged sexual misconduct by staffers during campaigns have become a larger and more visible issue in the wake of the #MeToo movement. In a head-turning interview earlier this year, Vermont Independent Sen. Bernie Sanders claimed he was too "busy" to know about the bombshell sexual misconduct allegations that roiled his 2016 presidential campaign, even as he apologized to any women who had not been "treated appropriately."

Sanders, widely considered a possible candidate for president again in 2020, was responding to a question from CNN anchor Anderson Cooper hours after a report Wednesday in The New York Times outlined what one former Sanders delegate called an "entire wave of rotten sexual harassment that seemingly was never dealt with."

The paper also included numerous complaints that women on the campaign were paid less than men and were frequently forced into inappropriate and uncomfortable situations.

Asked by Cooper whether he was unaware of the accusations, Sanders sarcastically replied: "Uh, yes. I was a little bit busy running around the country, trying to make the case."

And last year, former presidential candidate Hillary Clinton issued what left-leaning Vox.com called a "deeply unsatisfying" explanation for why she did not fire a staffer working on her 2008 presidential campaign who was accused of sexual misconduct.

Fox News' Alex Pappas and The Associated Press contributed to this report.