Mayor Ed Murray announced he intends to institute a citywide income tax on Seattle’s highest earners, and defend said tax in the State Supreme Court, potentially leading to an income tax statewide.

The mayor’s remarks came in his answer to a question about rising income inequality related to the tech sector, during the first mayoral debate of the election season, held by the 46th Legislative District Democrats at Seattle Mennonite Church April 20.

“We all know that Washington state has a regressive tax system,” Murray said. “We can all argue about what we’re going to do about it. These discussions have been going on since I was a kid in this city. What I’m going to send to council in the next few weeks is a proposal for a high-end income tax.”

As he said those words, a cheer and applause erupted from members of the audience.

“Now bear with me, it’s too soon to cheer,” Murray said. “It’s going to be challenged in court. But if we win in court … we can shift our regressive taxes, on sales tax and property tax, onto a high-income tax. We did it on minimum wage, we can do it on an income tax.”

Murray didn’t give any hints as to what income levels would be taxed, or by how much. But if his promise to send legislation in the next few weeks holds true, Seattle residents can expect to know those details sometime before summer.

Nor was it entirely clear how the tax would be assured a challenge in the State Supreme Court. Unlike California, Florida, Illinois, Massachusetts, Texas and West Virginia, Washington state law does not explicitly prohibit income taxes. However, that would not prevent a challenge from another party.

This wasn’t the first time Seattle residents had heard about a potential income tax in 2017. In January, the Transit Riders Union held a meeting to discuss an income tax proposal that would “Trump-proof” Seattle against punitive federal actions by the President Donald Trump Administration. At the March 1 meeting of the Seattle City Council, the Trump Proof Seattle coalition proposed a 2.5 percent tax on all households’ capital gains, and on the income of residents earning $250,000 per year or more.

If passed, Seattle would join a number of other major metropolitan cities that have an income tax, such as New York City, Birmingham, Alabama, and the District of Columbia. New York City taxes residents between 2.907 and 3.648 percent.

The announcement came in the first debate of the 2017 campaign for city mayor, as Murray prepares to defend his newly scandal-scarred incumbency against nine challengers.