If Sen. Gordon Smith (R-Ore.) were simply running for re-election against state Speaker Jeff Merkley (D), he’d probably be heading toward re-election. But he’s not.

Smith is also running against a political atmosphere that is among the most toxic for Republicans in decades, a GOP president whose Oregon approval ratings are below the 26.5 percent national average, a Democratic voter-registration advantage that has grown to nearly 10 points in 12 months, and a top-of-the-ticket tide that could see Sen. Barack Obama (D-Ill.) swamp Sen. John McCain (R-Ariz.) by double digits.

“I think this race is going to turn on how many Obama voters are going to go downballot and support Smith,” said Tim Hibbitts, an independent pollster based in Portland. “This race is still in play.”

As of Monday, the average of the last five polls taken in the race showed Merkley leading Smith 45 percent to 41 percent, with 8 percent undecided. Obama’s average lead over McCain was 15 points.

A new auto-dial poll released Monday and taken for a Portland television station by SurveyUSA had Merkley leading Smith 49 percent to 42 percent, with 4 percent undecided and 5 percent choosing Constitution Party candidate Dave Brownlow. Brownlow, a libertarian-style conservative, is considered enough of a problem for Smith that the Senator recently went on television with an ad critical of the third-party candidate.

Merkley began to exhibit a narrow lead in the polls only in mid- to late September, and that trend has continued.

Still, the knock on Merkley is that he has yet to close the deal. One Democratic strategist said voters still don’t know who he is, suggesting that Merkley is benefitting in large part from the “D” next to his name and Obama’s strength in Oregon.

In perhaps a tacit acknowledgement of that analysis, the Merkley campaign late last week began running a television ad on statewide broadcast and cable television featuring Obama talking straight to the camera and urging voters to elect the Oregon Speaker.

“Oregon, you have a choice,” Obama says in the 30-second spot. “Do you stick with the failed Washington policies that put CEOs and special interests first, or do you choose real change? That change is Jeff Merkley.”

Still, Smith, despite the several obstacles standing between him and a third term, remains in the game.

Smith has always performed well with independent female voters, and his reputation as a pragmatic moderate who crosses party lines — particularly to work with popular Sen. Ron Wyden (D-Ore.) — is well-established.

The Merkley campaign describes Smith’s reputation for bipartisanship as the “Smith myth,” calling it the only factor in Smith’s favor with Election Day one week away.

Smith, who today is scheduled to begin a statewide bus tour to close out the campaign, has advertised heavily to inform voters of legislation he has co-sponsored with Obama and the work he has done for Oregon in conjunction with Wyden. Even some Democrats concede Smith’s reputation for moderation and bipartisanship is solid enough with Democrats and independents that he could yet win re-election.

“What Oregonians are craving right now is change and a breakthrough from the partisan gridlock paralyzing Washington, D.C.,” Smith campaign spokeswoman Lindsay Gilbride said. “The only candidate who embodies bipartisan leadership is Gordon Smith.”

The Merkley campaign, however, insists it is better positioned to capitalize on the Oregon electorate’s desire for change in Washington, D.C. — and it is buoyed by what it feels is a better ground game anchored by a strong in-state presence by the Obama campaign.

Because Oregon is a mail-only voting state, political parties and partisan third-party groups are able to track ballot returns and specifically target those desired registered voters who have yet to mail in their ballots.

Beaver State Democrats, aided by organized labor, tend to do a better job of targeting their partisans and getting them to mail in their ballots than do the Republicans.

Democrats monitoring ballot returns say enrolled voters in their party have outpaced Republicans thus far by about 10 percent. Democrats also contend the Obama campaign’s turnout operation far exceeds the effort of the Smith campaign and the Republican National Committee’s Victory Program, although the Smith campaign argues its grass-roots network is vast and effective.

The Merkley campaign dismisses suggestions that its candidate is headed toward victory simply because the Democratic Party and Obama are more popular than the GOP and McCain.

Merkley’s team argues that the Democrat has outlined an agenda that focuses on the single most important issue on voters’ minds — the economy — and that is why Smith is headed toward retirement.

Merkley is now pushing for Congress to return to Capitol Hill for a lame-duck post-election session in order to pass an economic stimulus package that includes a retroactive tax cut for middle-income earners.

“It will be a close election,” Merkley campaign spokesman Matt Canter said. “But there’s no question that Oregon wants change, and Jeff Merkley is the candidate of change.”