The Oregon Supreme Court on Thursday ruled unanimously that campaign contribution limits passed four years ago by Multnomah County voters are constitutional.

Prior to the ruling, Oregon was one of just five states that didn't place a limit on campaign contributions.

In 2016, Multnomah County voters overwhelmingly passed a ballot measure to limit campaign contributions and expenditures, but opponents of the measure— including the Portland Business Alliance, the Portland Metropolitan Association of Realtors, and Associated Oregon Industries (now Oregon Business & Industry)—appealed.

Oregon Supreme Court Chief Justice Martha Walters wrote the opinion upholding the contribution limits, a decision that overturns the court's 1997 ruling in VanNatta v. Keisling.

The ruling is a major victory for campaign finance reformers led by lawyers Dan Meek and Jason Kafoury and advocates that include Liz Trojan, Ron Buel, Seth Woolley and David Delk, who have long fought to get big money out of politics.

The next step is for the case to be sent back to Multnomah County Circuit Court, which will decide whether the contribution limits are constitutional under the First Amendment, county spokeswoman Julie Sullivan-Springhetti said in a press release.

It is highly unlikely the Multnomah County court will rule prior to the May 19 primary. But today's decision could alter November general election dynamics significantly.

One thing won't change: Today's ruling upheld a lower court decision that the reformers' attempts to place limits on independent expenditure campaigns cannot stand. That means even if candidates are soon limited in how much they can raise and spend, their supporters will not be.

Gov. Kate Brown addressed the ruling during an unrelated press conference April 23.

"As someone who's been working to bring reasonable campaign finance to Oregon for over 20 years, I was certainly pleased to see the ruling of the Oregon Supreme Court this morning," Brown said Thursday. "I think this moves to more of a case-by-case determination in terms of whether limits are reasonable. It is my plan at this point in time, once we're beginning the reopening work, that I will continue our efforts to amend Oregon's constitution…to clarify that we do have the ability, either through the Legislature or by the people, to enact reasonable campaign finance limits in Oregon."

Senate Majority Leader Ginny Burdick (D-Portland) said in a statement she was pleased with the ruling.

"The Oregon Supreme Court made the right decision today," Burdick said. "Campaign contribution limits will protect our democratic process and allow elections to be more competitive and inclusive. This ruling will strengthen the voices of every day Oregonians and ensure a representative government."

County commissioners also expressed support for the ruling.

"We know that big money pollutes politics, and I'm glad that Multnomah County could play a part in rectifying that,'' Commissioner Lori Stegmann said in a statement. "We must create a structure that allows everyone to have a fair chance to lead and encourages diverse perspectives at the decision-making table."

"Today's ruling is historic,'' Commissioner Susheela Jayapal said. "By clearing the way for contribution limits, it allows us to limit the influence of money in Oregon politics, strengthens our democratic processes, and returns power to the voters."