Portland voters have passed a campaign finance measure that limits large contributions in political campaigns and requires candidates in city elections to disclose their funders in advertisements.

The measure, which amends the city charter, was passing with 87 percent of the vote in favor and 12 opposed in unofficial returns as of Tuesday night.

It could set Portland squarely in the middle of a statewide fight over campaign finance limits.

Oregon is one of only five states with no limits at all on political contributions, despite decades of effort by campaign finance activists.  

The Portland measure bars political contributions from corporations and limits the amount a candidate can receive from an individual donor to $500. Individuals can give no more than $5,000 total to city candidates and initiatives per election, while political committees can make aggregate contributions of no more than $10,000 per election.

Small donor committees — groups that limit individual contributions to $100 — are exempt from those limits.

The limits are essentially the same as campaign finance measure adopted by Multnomah County voters in 2016 with 89 percent approval. 

A Multnomah County judge ruled earlier this year that those contribution limits violate the free-speech protections in Oregon’s Constitution. That ruling was based on a 1997 Oregon Supreme Court decision that struck down statewide campaign finance limits.

The county measure’s backers are appealing that decision, arguing that the free speech provision in Oregon’s Constitution is not unique and that many states with similar free speech protections limit political spending.

Meek says passing campaign finance limits by a wide margin in the most populous city and county in Oregon is part of a broader strategy to challenge that 1997 Supreme Court ruling.

That strategy could include another effort to amend the state’s constitution to allow political spending limits.

In 2006, Oregon voters rejected a constitutional amendment that would have allowed limits on political spending.

Separate from the campaign finance limits, which are vulnerable to a legal challenge, Portland recently adopted a public finance system for campaigns that is set to roll out in 2020.

It was championed by Commissioner Amanda Fritz and adopted by a Portland City Council vote, rather than by voter approval.

The city will provide matching funds to eligible candidates for mayor, city commissioner and auditor, with funding starting in 2019 for the 2020 election.

To qualify for the public matching dollars, candidates for mayor will have to raise at least $5,000 from 500 individuals. Candidates for commissioner or auditor would have to raise at least $2,500 from 250 people.

In exchange for agreeing to limit individual contributions to $250 or less and abiding by other fundraising limits, qualified candidates will receive a 6-to-1 match for campaign contributions of $50 or less.

Portland has had an on-again, off-again relationship with publicly funded campaigns.

Voters repealed Portland’s previous attempt at publicly funded elections in 2010, after a high-profile case of fraud.