Eight months after Phoenix voters approved an amendment to outlaw the use of "dark money" in city elections, it officially became law this week.

The City of Phoenix was notified Wednesday by the governor's office that the amendment had received final approval, Phoenix Mayor Kate Gallego announced on Twitter.

The amendment had been under legal review, a spokesperson for Gov. Doug Ducey told The Arizona Republic in March.

The law requires individuals and organizations to disclose any campaign donations valued at more than $1,000 that are intended to influence a Phoenix election.

Gallego said on Twitter that the city had pushed the governor's office for eight months to approve the amendment.

"This is a momentous day for our city, she said on Twitter. "For far too long, we have allowed political operatives to exist in the shadows, wielding influence over city elections without having to reveal their true identities."

What is 'dark money?'

Negative ads not connected with the candidates and their campaigns were a staple of the recent mayoral election. A recorded phone call suggested Gallego supports calling police officers murderers and Nazis. A mailer showed Gallego's opponent, Daniel Valenzuela, on a $100 bill covered in blood.

TV commercials painted Valenzuela as a waster of tax dollars and Gallego as a danger to public safety.

Dark money groups do not reveal who they are, and election law does not allow candidates to be connected with them.

Prop. 419 had bipartisan support

In November, voters approved Proposition 419, which forces outside groups that are trying to influence elections to reveal their donors.

"With this charter amendment, we can shed light on vested interests & carry out the will of PHX voters," Gallego said on Twitter. "I pushed to stem the flow of dark money into our city b/c Phoenicians deserve to see political discourse conducted in a way that is clear & accessible to all. Today is for them."

When Gallego and Valenzuela were on the City Council, a bipartisan majority of the council referred the measure to the ballot.

The Greater Phoenix Chamber of Commerce was against the proposition, according to a report by The Republic.

"It has the potential to open up the chamber's and other nonprofits' finances to groups that disagree with positions these groups take in regards to candidates or ballot measures," the organization website stated before the 2018 election. "Additionally, this effort will effectively suppress the business community's speech in elections."

Republic reporter Jessica Boehm contributed to this article.

Have thoughts about Arizona’s legal system? Reach criminal justice reporter Lauren Castle at Lauren.Castle@gannett.com. Follow her on Twitter: @Lauren_Castle.

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