With five days left until the May 21 election, polling numbers keep getting worse for fluoride.

Ballot Measure 26-151, which would fluoridate Portlands water supply, trails by 13 percentage points in the newest poll released by WW's news partner KATU, with 53 percent of likely voters saying they'll vote no.

Fluoride is losing even though the pro-fluoridation campaign, Healthy Kids Healthy Portland, has outspent the anti-fluoridation campaign, Clean Water Portland, by a two-to-one margin

The math gets even worse for the fluoridation campaign among people who have already mailed in their ballots. Among those voters, fluoride trails by 24 percent.

You can read the details of the poll, conducted by SurveyUSA of 800 Portlanders, here.