I assume this goes to the Oregonian's continued warped sense of "balance" since they had endorsed Barack Obama the day before. Objectivity requires splitting the baby right down the middle. They have readers in the blue and the red part of the state after all. Except they really don't...
Like most states Oregon has concentrated population areas around big cities surrounded by larger tracts of rural, sparsely populated counties and towns. The urban area of Oregon stretches down through the Willamette Valley from Portland to Eugene. This is the area of the state viewed with derision by many rural Oregonians because it's generally more progressive and tends to favor Democrats. It also happens to be the area where the bulk of the Oregonian's readership resides.
When the Oregonian pulls one of these bone-headed stunts such as endorsing George W. Bush over Al Gore or, more recently, publishing the anti-Islamic "Obsession" video and now endorsing Smith they're directly insulting their readers. They're saying to their readers that those that run the paper are smarter than those that pay to read it.
What business can survive by insulting it's customers in such a direct manner and on such a regular basis? If you went to a deli where you were told you couldn't have the tuna because "people who eat tuna are morons" would you go back to that place?
As the readership of the Oregonian continues to decline I'm sure they'll have all sorts of excuses as to what's killing their business. They'll blame the rise of cable/ satellite. They'll finger the Internet. They'll claim it's the rise of progressive partisanship made it impossible to sell papers.
The answer will be much simpler. They simply aren't catering to their customers.