State prosecutors, who examined de Blasio's unsuccessful 2014 effort to help Democrats regain control of the state Senate, concluded that the aspects of the undertaking amounted to an "end run" around limits on contributions to candidates, according to a 10-page letter outlining their findings.
For more than a year, de Blasio has faced down the barrels of investigations into how he raised money and what that money bought.
Kim noted the unusual nature of announcing that his office wouldn't pursue criminal charges, saying that, in this case, it was appropriate to not "unduly influence the upcoming campaign and Mayoral election".
Vance recommended revised laws that would make it impossible for candidates or officeholders to circumvent donation limits and reporting requirements to raise money for general objective policy-oriented campaign committees, as de Blasio did in his first two years as mayor.
The decision not to prosecute, Kim said, was made based on several factors, including "the particular difficulty in proving criminal intent in corruption schemes where there is no evidence of personal profit".
Federal and state prosecutors said Thursday that Mayor Bill de Blasio will not face prosecution in two almost yearlong campaign-fundraising probes. "We have been confident from the moment these reviews began that the actions of the Mayor and our Administration have always been within the law", Phillips said.
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At a news conference, de Blasio said he disagreed with some characterizations in the prosecutors' statements.
Nor that Manhattan DA Cy Vance said outright that de Blasio & Co. had violated "the intent and spirit" of state campaign-finance laws. In February, Mr.de Blasio himself was called in for four hours of questioning. De Blasio's actions on that front were within the law. The US attorney's office and the FBI conducted the federal investigation, and the Manhattan district attorney's office oversaw the state one, assisted by the FBI.
After months of investigating, city and federal prosecutors have decided not to bring corruption charges against Mayor Bill de Blasio.
The money was then transferred to the candidate groups, which then used them on things like consultants and media advertising, a shift that "often occurred within days", Vance said.
The two probes were conducted by federal prosecutors and by Cyrus Vance, the Manhattan district attorney.
Acting U.S. Attorney Joon Kim announced no charges against Mayor Bill de Blasio or others acting on his behalf.