With a little more than one week to go before the May 21 Special Election, only around 11 percent of Multnomah County voters have mailed in their ballots.

That’s a surprisingly low return rate so far, given the highly visible campaigns being waged over the measure to fluoridate Portland’s water. Around three-quarters of all registered voters in the county live in Portland. And more than 36 percent of county voters mailed in their ballots in the May 17, 2011, Special Election, which did not have any controversial measures on the ballot.

The two campaigns have so far raised over $920,000 in cash and in-kind contributions. The committee in support of Ballot Measure 26-151 currently reports more than $684,000 in donations. The committee opposing fluoridation has raised more than $235,000.

Two other measures on Portland ballots are also drawing significant support. The committee in favor of Measure 26-151, which extends the Portland Children’s Levy, reports raising more than $369,000. The committee in favor of Measure 26-152, to help maintain Metro’s open spaces, has raised over $247,000.

The rate of returning ballots should increase steadily over the next week. Both sides in the fluoridation fight have volunteers going door to door to identify supporters and makes sure they vote.

Voters have until 8:00 p.m. next Tuesday to return their ballots to a county elections office or officially designated drop off site.