On Sunday afternoon, 75,000 supporters padded down to the Waterfront Bowl in the fair city of Portland, Ore. for the Illinois senator’s largest rally to date. Sixty thousand got in; the remaining 15,000 watched from outside the gates. The opening act was The Decemberists, a bespectacled indie-rock band that laces its bookish songs about legionnaires and architects with words like “palanquin” and “fontanelle”; John Mellencamp they are not. With its backdrop of twee little tugboats and sprawling audience of mellow, well-read young urbanites, the event neatly reinforced the conventional wisdom–i.e., that the Beaver State is a progressive paradise ripe for Obama’s taking in tomorrow’s primary. And the polls agreed. By the time Obama appeared on stage in his shirtsleeves, no survey taken since the start of May showed the Democratic frontrunner with anything less than an 11-point lead over Hillary Clinton. The latest poll pegged his margin at 20 percent.

But this morning a pair of new surveys suggested that Obama’s advantage had shrunk dramatically in the week since the previous round of soundings. The first stats to hit the wires, from Suffolk, gave Obama a measly four-point edge (45-41), and American Research Group’s five-point margin (50-45) wasn’t particularly encouraging, either. Coupled with the photos of that sea of Obama adoring supporters in Portland, the new numbers got me wondering: Could Obama’s self-evident strength in the microbrew-drinking, tree-hugging, telecommunitng western third of the state be masking the fact that the rest of Oregon–rural, older, more conservative–is breaking for Clinton? Could the former first lady actually beat expectations on Tuesday?

In theory, at least, it’s possible. In demographic and cultural terms, Oregon has a lot in common with its neighbor to the north, Washington state. There, Obama clobbered Clinton 68-31 in the only contest that mattered–the Feb. 9 caucuses–and most analysts have predicted a similar blowout in Oregon. But while Washington awards its delegates solely on the basis of those caucus results, it also holds a primary–a meaningless primary, but a primary all the same. The results from that Feb. 19 face-off? 51-46 Obama–a mere five-point margin, which mirrors the Suffolk and ARG surveys for Oregon. Obama has always done well in caucuses, which reward on-the-ground organization and activist zeal. But on Tuesday, Oregonians are participating in primary–and that alone could give the Clintonites some (ahem) hope.

That said, I’d caution against reading too much into the Suffolk and ARG surveys. For both firms, these latest polls represent their first attempts to sound out Oregon this cycle–never a confidence booster. Meanwhile, two outlets with more recent experience in the Beaver State released surveys today that contradict the “Clinton is gaining” storyline. Public Policy Polling’s second survey of the season shows Obama expanding his lead from 14 points to 18, and SurveyUSA, now on its fourth poll since April, gives Obama a 13-point advantage (up from 11 on May 10 and six late last month). If Clinton does give Obama a run for his money, she’ll have her usual supporters–women, seniors and whites–to thank. In the SurveyUSA poll, Obama manages to tie Clinton among women and voters over 50, then trounces her by nine among Caucasians. But ARG has the New York senator beating her rival by seven in the geriatric division, seven among the ladies and finishing a few points closer on the lighter-skinned side of the ledger as well. Those differences pretty much account for the eight-point gap between the polls. Still, according to the New York Times, “the vast majority of new voters who have registered this year are Democrats, and well more than half are 30 or younger, a group that has embraced Mr. Obama.” Seeing as those folks haven’t been factored into the latest likely-voter models, Clinton probably shouldn’t cross her fingers.

In the end, though, Obama’s massive rallies and polling resilience are probably good news for Hillary, at least in the local expectations game. No matter what happens tomorrow in Oregon, her chances of clinching the Democratic nomination are vanishingly, impossibly microscopic. With that in mind, it’s far better to beat the odds with a surprising show of strength than to raise everyone’s hopes with sketchy stats–and then fall short on Primary Day. So Clinton should be thankful that no one’s paying too much attention to the Suffolk and ARG surveys, or to the fact that Bill has quietly spent the past few weeks scurrying from one rural Beaver State hamlet to another–Scappoose, Milwaukie, Hood River, Tillamook–in search of every available vote. If Clinton loses by double-digits tomorrow, so what? Everyone knew it was coming. But in the unlikely case that she comes closer, she suddenly has one more reason (in her book, at least) why she should be allowed to “make [her] case” until the voters of Montana and South Dakota cast their ballots on June 3.

UPDATE, 6:49 p.m.: Also worth nothing: Oregon votes entirely by mail–meaning the results are largely (to coin a phrase) signed, sealed and delivered at this point. According to PPP, Obama “is likely to win a dominant victory tomorrow in Oregon. In fact, “given how many people have already voted and how strongly they’re going for Obama, there’s a decent chance he’s already won the primary based on the ballots already filled out. 74% of respondents said they had already voted, and among them Obama has a 60% to 39% advantage.” In comparison, only one-third of Suffolk respondents said they’d voted–even though about two-thirds of Oregonians overall had mailed in their ballots at the time of the survey. That should tell you something about the accuracy of their stats–and hint at the size of Obama’s victory.

More analysis: “PPP has repeatedly found similarities between Wisconsin and Oregon in its polling of the two states. Both times polling more than two weeks out tended to show Obama with a lead in the single digits. A week out his lead moved into the lower double digits. And now it’s in the upper double digits. Oregon is also the only state besides Wisconsin where we’ve found the war as an issue on par with the economy, and that works to Obama’s advantage as well.”