Oregon’s upcoming special election is the GOP’s best chance in decades of picking up Oregon's 1st House district. But the party’s nominee must win Washington County, a crucial battleground that’s favored Democrats.

The 1st district, formerly represented by disgraced Democrat David Wu, has not had a Republican congressman since the Watergate election of 1974. While history has shown the race is a quixotic challenge for any Republican, some results from recent specials in New York have given the party hope of winning a hugely symbolic victory here.

The district has a partisan voting index of D+8, which makes it two points more Democratic than the most Democratic seat a Republican currently holds -- Illinois Rep. Bob Dold’s seat -- and three points more Democratic than former Rep. Anthony Weiner’s old district in New York, which Democrats lost after he resigned in disgrace.

National Democrats have taken the vote slated for Jan. 31 seriously. The Democratic Congressional Campaign Committee has put $744,000 on Portland broadcast TV through Election Day. The buy may have been prompted by a realization that there has been a recent trend toward punishing the party of a disgraced member in a special election -- think Weiner’s seat going to now-Rep. Bob Turner (R) or former Rep. Chris Lee’s (R) seat going to Democrat Kathy Hochul.

But it isn’t just recent trends that will dictate the outcome of the Oregon special. Here’s how geography could factor into the race, which pits former state Sen. Suzanne Bonamici (D) against Republican businessman Rob Cornilles.

The core of the district is Washington County, the largest suburban county in the Portland area. Bonamici and Cornilles live in Washington County, and it accounts for two-thirds of the district’s population. Last time around, Cornilles earned 45 percent here on his way to an impressive showing against Wu. Meanwhile, 2010 Republican gubernatorial candidate (and former Portland Trail Blazer) Chris Dudley lost the county by 1.5 points -- the same margin by which he lost the state.

A Republican hasn’t carried Washington County in an election of consequence since then-Sen. Gordon Smith won it in a largely uncontested reelection campaign in 2002. While the county leans Democratic, it’s not solid blue and it has the potential for a good Republican candidate to carry it.

Still, Cornilles would have a much better chance of winning this district if 10 percent of it didn’t extend into Multnomah County, where Portland is located. The city likely has more microbreweries than Republicans, and in their 2010 contest, Wu got 78 percent of the vote in the Multnomah County portion of the district. Half of Wu’s margin of victory came in this small part of the district. The inclusion of such an overwhelming Democratic area is a major barrier to a Republican victory.

The GOP base in the district is Yamhill County, which is mostly rural and dotted with small towns. It’s the only county Cornilles won last cycle, but unfortunately for him it’s only 12 percent of the district. The district also includes Clatsop and Columbia Counties, which combined account for about 10 percent of the population, and are politically marginal. 

To win, Cornilles has to win Washington County outright. Outright victory is necessary because he cannot allow Bonamici to add to the margin she will earn from Portland. He also must bank on strong support in the other counties to offset the Democratic vote margin in Portland.

Cornilles could take some comfort from the experience of Turner. He ran a strong but unsuccessful challenge to Weiner in 2010, and when Weiner resigned his seat, Turner was able to build on that experience and win an upset victory. But Cornilles has to hope that Bonamici runs an error prone campaign like Democrat David Weprin did in New York. So far, there is little evidence that Bonamici is as inept.

Chris Palko works as an assistant media analyst at Smart Media Group, a Republican political media buying agency in Alexandria, Va. He is a graduate of American University and George Washington University’s Graduate School of Political Management.

A version of this post was also published on Smart Media Group’s blog, Smart Blog.