[1] 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.

Of these, 52 pledged delegates were allocated proportionally to one of the Democratic presidential candidates in the primary.

)[3] The 52 pledged delegates were allocated as follows:[3] Oregon also had 13 unpledged superdelegates, all of whom endorsed Obama (though Kulongoski and Hooley originally endorsed Clinton in the primaries):[4][5] On May 18, 2008, Barack Obama addressed a rally in Tom McCall Waterfront Park in Portland, with a crowd estimated at 72,000 (60,000 inside the gates and another 12,000 outside).

[17] This crowd was the largest ever to greet Obama, surpassing his previous record of 35,000 people in Pennsylvania.

[17] Large, media-attracting rallies and meetings such as this were noted to make a substantial difference in electorate enthusiasm and volunteer sign-ups for both Democratic Party potential candidates.