Portland Mayor Ted Wheeler trails his challenger Sarah Iannarone by 11 points, according to a poll of likely voters conducted by DHM Research on behalf of the Portland Business Alliance.

The results were presented at a PBA meeting last week.

Wheeler polled at 30% to Iannarone's 41%, with the remaining 29% of surveyed voters split between writing in a candidate (16%) or remaining undecided (13%). It's an especially notable result given that the poll was not conducted by either campaign, though PBA is supporting the mayor. (The poll has a four percentage point margin of error.)

The results are somewhat surprising given that Iannarone finished more than 20 points behind the mayor in the primary, in which Wheeler nearly received the 50% plus one of votes required to avert a runoff.

At the same time, Wheeler has faced intense criticism throughout the summer for his handling of protests and policing. And another recent poll, conducted on behalf of a City Hall police accountability measure, had Wheeler at 26% favorability, The Oregonian reported.

The DHM phone survey, conducted from Sept. 17 to 22, also found that all the city and county measures presented to Portland voters are likely to pass. These include tax measures to build new libraries, maintain parks and renovate school buildings, as well as fund tuition-free preschool.

Update 5pm: The mayor's campaign said internal polling shows the mayor will win in November.

"Our internal polling shows that we're in position to win and that we have a clear path to victory," says Wheeler campaign spokesman Danny O'Halloran. "Most voters are just tuning in to this race, and that's why such a large number of respondents in this poll are undecided. We are confident that once voters have the opportunity to get to know both candidates, these numbers move decisively in Ted's direction."

Iannarone tweeted the story, and says she now expects "opponents of progress to do everything they can to try and block this historic grassroots campaign."