Dr. Monica Wehby and state lawmaker Jason Cogner are the two leaders in the race.
A lot of negative stories have come out in the last week regarding Wehby and harassment charges leveled against her from an ex-boyfriend and ex-husband.
Political Science Professor Jim Foster says he doesn't believe it will play much of a role in the primary because a lot of people had already voted by then.
"It's hard to know what to make of all of that. Here is a person that has made a big deal of the fact she's a medical doctor and knows the medical profession and is against the Affordable Care Act. It's unseemly and runs counter to her professional demeanor when two, not one former partners accuse her of this curious behavior I would say."
Whoever wins the Republican primary Tuesday will face Senator Merkley in November.