The Democratic voters are considered progressive, post-partisan and reform-minded. Every member of the state's Democratic congressional delegation voted against authorizing the use of force in Iraq. It's one of the least diverse states in the country, but not one where race generally comes into play in politics, said Mark Wiener, a Portland-based Democratic political consultant.
And Oregon never turned out overwhelmingly for former President Bill Clinton, who won the state with 43 percent of the vote in 1992 and 49 percent in 1996.
"Oregonians seem to like the cool, cerebral type," Oregon pollster Tim Hibbitts said. "They liked Harding. They liked McCarthy. They liked McGovern. They seem to like that kind of Democrat. And, without putting an ideological implication on it, I think that Obama stylistically appeals to Oregonians."
All of this portends a strong showing for Obama in Tuesday's mail-in primary. A better-than-expected performance for Hillary Rodham Clinton would do wonders for her campaign, but few, if any, Oregon political experts predict such an outcome.
Here is what Oregon political strategists and experts will be watching Tuesday:
How quickly is the race called? Good news for the East Coast-based TV networks: Oregon, already three hours behind on Pacific Standard Time, isn't expected to take long to count the mail-in ballots because of their electronic tabulating machines.
The ballot counting begins in the morning and the first unofficial results are released at 8:00 pm local time. They will continue to be updated until all the ballots have been counted. According to the Secretary of State's office, 727,527 ballots had been returned through Sunday.
Be careful not to read too much into the early tabulations, which are likely to heavily favor Obama because they will come out of Portland and Multnomah County, said Paul Gronke, a Reed College political science professor.
The showing in the strongholds. Heavy voting in Portland and surrounding Multnomah County are a good sign for Obama. He is expected to beat Clinton by a 2-to-1 margin in this metropolitan area "full of young Democrats under the age of 35," said William Lunch, a political analyst with Oregon State University.
Clinton needs to perform well in southern Oregon and east of the Cascade Mountains - areas that are considered more rural and conservative. Following the strategy followed in other states, that's where Clinton sent her husband to campaign. Look to Bend's Deschutes County, Medford's Jackson County and Pendleton's Umatilla County, experts said.
"If [Obama is] winning all of those, he's going to roll up a big margin," Hibbitts said.
How goes Marion County? The county, which is home to more than 300,000 residents and the state capitol of Salem, has yielded votes within 5 percentage points of the actual statewide primary results in 1988 and 2000 - the last elections with no incumbent president on the ballot. There is a mix of income levels in the area, from upscale liberals to blue collar workers.
Clinton needs to win this county by almost double digits if she has any hope of taking the state, said Lunch.
Follow the demography. Political observers expect women to comprise as much as 58 percent of the statewide vote. That would appear to be a promising sign for Clinton, but polls in Oregon have shown Obama leading among women voters.
West of Portland, Washington County will be a good gauge of suburban female voters. If Clinton has strength in the state other than in rural and small-town areas, she could find it in this county, said Wiener.
To test Obama's support among blue-collar Democrats, look to heavily industrialized Albany in Linn County about 70 miles south of Portland, Hibbitts said.
Obama should do well in the blue-collar counties "relative to Ohio and Pennsylvania," Hibbitts said. "I'm not saying he's going to win those counties, but I thik he may win some of them. He may win a significant number. And he won't get beat 3-to-1 the way he did in Pennsylvania in some of those counties. Here, I think he'll be very competitive, even in the places that he might lose."
For a glimpse at the Hispanic vote, look to Woodburn in Marion County, where half of the 20,000 residents are Latino. Good advance work led Obama to eat lunch at a local Mexican restaurant there earlier this month.
To measure college activity, keep an eye on Corvallis in Benton County. Home to Oregon State University and high-tech workers at the major employer, Hewlett Packard, Obama should win the area by a 2-1 margin, Lunch said.
What's the turnout? With the presidential primary and closely contested Democratic primaries for U.S. Senate (the seat held by Republican Gordon Smith), attorney general and secretary of state, experts are predicting a "turnout" of 60 percent or more. In Oregon, which conducts elections by mail, the measure of turnout is actually the percentage of ballots returned.
"I think we're going to have the highest Democratic primary here that we've had probably in 40 years and that was the Kennedy-McCarthy primary in '68," Hibbitts said, "and that was really the last time Oregon actually mattered in presidential politics."