Oregon Revised Statutes Miscellaneous Matters Related to Government and Public Affairs § 188.120

(1) If a vacancy in election or office of Representative in Congress or United States Senator occurs before the 61st day before the general election, the Governor shall call a special election to fill that vacancy. If a vacancy in election or office of United States Senator occurs after the 62nd day before the general election but on or before the general election, and if the term of that office is not regularly filled at that election, the Governor shall call a special election to fill the vacancy as soon as practicable after the general election.

(2) If a special election to fill the vacancy in election or office of Representative in Congress or United States Senator is called before the 80th day after the vacancy occurs, each major political party shall select its nominee for the office and certify the name of the nominee to the Secretary of State. The Secretary of State shall place the name of the nominee on the ballot.

(3) If a special election to fill the vacancy in election or office of Representative in Congress or United States Senator is called after the 79th day after the vacancy occurs, a special primary election shall be conducted by the Secretary of State for the purpose of nominating a candidate of each major political party. A declaration of candidacy or nominating petition may be filed not later than the 10th day following the issuance of the writ of election.