Portland returned to publicly financing candidates for the first time since 2010. One result? Taxpayer dollars made the mayor's race competitive.

Mayor Ted Wheeler, seeking to break the city's streak of one-term mayors, sought reelection. Four years ago, Wheeler easily captured the 50 percent plus 1 required to avert a November runoff, winning 55 percent of the vote in a field of 15 candidates.

But this time, his share of the primary vote was 49.29 percent, just missing the mark, despite the advantage an incumbent usually enjoys. Sarah Iannarone pushed him to a November runoff.

Iannarone was the one contestant in the mayor's race to sign up for the public financing program, which matches contributions of $50 or less by 6 to 1. (The total cost this election: $1.8 million.) She received $330,892 in public financing—more than any other candidate in the program because she received the most small donations.

She won 23.8 percent of the vote—far less than Wheeler but enough to force a runoff, and double the nearly 12 percent she got last time.

Iannarone's campaign manager Gregory McKelvey disputed the idea that public financing buoyed her bid. "I believe the impact of public financing is not that everyone who qualifies becomes competitive," he says, "but rather, anyone who qualifies is then free to hear from working-class Portlanders rather than spending the bulk of their time speaking with the extremely wealthy."

If public financing propelled a leftist mayoral candidate to the general election, it had the opposite effect in the race for a Portland City Council seat in which nine candidates received public funding. That created a crowd of candidates seeking the progressive lane, including Tara Hurst, Julia DeGraw and Margot Black. None broke 15 percent.

The return of public financing didn't get complete buy-in. Wheeler didn't participate and relied on big-money donors. (In future, that may be less of a factor, because campaign contribution limits approved by voters in 2016 are likely to be in place, giving all candidates an incentive to participate in the public funding system.) And supporters of former Mayor Sam Adams' bid for the City Council evaded the caps—even though Adams participated in the program. Adams' supporters spent more than $100,000 on independent expenditures to support his candidacy. It didn't work: Adams finished third, out of a November runoff.