the 2008 oregon democratic primary was a mail-only primary in the u.s. state of oregon. ballots were mailed to registered democratic voters between may 2 and may 6, 2008. to be counted, all ballots had to have been received by county elections offices by 8:00 p.m. pdt on may 20, 2008. it was a closed primary and voters had to have registered as democrats by april 29, 2008 to be eligible to vote in any of the partisan races.