The race is shaping up to be a strong test of the GOP strategy of relentlessly using the health law against Democrats in hopes of regaining control of the Senate.
The rollout of the law in Oregon has been worse than in most other states, and Republicans are hoping a doctor has the credibility to capitalize on the resulting voter discontent.
"Doctors are trained differently," Wehby said in a recent candidate forum at a Republican women's club in Lake Oswego, a well-to-do Portland suburb. "We know how to look at things logically, not ideologically, and we also know how to work with other people."
Ballots go out April 30 in the state's all-mail primary and must be returned by May 20, when they will be counted and results announced.
Wehby faces four other Republicans, most notably state Rep. Jason Conger of Bend, a lawyer who's promoting his conservative credentials and his experience representing a district that, like the state as a whole, favors Democrats.
The Republican nominee will face long odds against the incumbent, Democrat Jeff Merkley, who's in his first term. Merkley used Obama's coattails to slip past GOP Sen. Gordon Smith in 2008.
Eight months before the November general election, Merkley rates as the favorite, based on the Democrats' 8-point edge in voter registration and the GOP's longstanding weakness in statewide elections.
If Republicans can put the seat into play, it would boost their efforts to reclaim the Senate. They need a net gain of six seats to hold a majority.
"I want someone that I feel has enough support to have a realistic opportunity of winning," said Marge Mares, 70, a Republican from Portland. "It would be wonderful if the Republicans can take back the Senate."
Mares, who owns a steel business with her husband, said the health law is her "number one concern."
No Republican has won a statewide race in Oregon since Smith was re-elected in 2002. In 36 statewide partisan elections over the past two decades, said Portland pollster Tim Hibbitts, Republicans have won just three, and none of the last 19.
But Merkley does have some obstacles to overcome.
It's a midterm election, which often means lower Democratic turnout.
Also, Wehby, in particular, could attract a lot of money from deep-pocketed donors. Empowered by U.S. Supreme Court decisions, out-of-state donors have been putting money into campaigns in Oregon, a small state where contributors believe their money will have more impact.
Merkley's prospects are linked to voter attitudes toward Obama, Hibbitts said. "What Obama's approval is in Oregon on Election Day is more important to me right now, frankly, than anything Merkley has or hasn't done."
Wehby, 51, has kept her eye on the general election, taking moderate positions on social issues that are in line with a majority of Oregon voters and betting that her advantage in campaign cash can get her through the primary. She supports same-sex marriage and says the federal government shouldn't be involved in abortion, although she says she's personally opposed.
Wehby insists she's concerned about more than just "Obamacare." She says the health law is an example of an overreaching federal government "that is encroaching on every aspect of our lives." But the issue is at the heart of her pitch to voters.
"It's not brain surgery," she says, dressed in surgical scrubs for a television ad that aired last week. "Obamacare is bad for Oregon." The ad never mentions she's a Republican.
Wehby appeared in television ads opposing the law in 2009. She later was part of a faction of the American Medical Association that rebelled against the group's support for some aspects of the law.
She calls for repealing the Affordable Care Act and enacting something else, a common theme among Republican office-seekers. She said she doesn't think "we can go back to the way things were before."
Conger, 45, is running to Wehby's right. He says her stands on social issues are out of step with the Republican Party, and pitches his own experience winning elections in a Democratic district.
"I've won by really significant margins," Conger said in an interview. "And the only way that could happen is, I've demonstrated the ability to reach out to voters who are not already convinced, not already Republican, and persuade them that I will do a better job. I think that's important for the Republican nominee."
Conger's life story is a rich political narrative. From a hardscrabble childhood in California — "I still remember what it's like to live in a trailer park," he says — he managed to put himself through Harvard Law School.
"I believe that I have the ability to relate to people who are not rich, to express conservative solutions, a conservative approach to solving problems in a way that... has relevance for their situation," Conger said.
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