1990 United States Senate election in Oregon

In the Republican primary, Hatfield received a token challenge from Randy Prince, an environmentalist and former Eugene mayoral candidate who had once protested old-growth forest logging by tree sitting for 40 days.[2] Despite an early miscue by Hatfield in which he missed the deadline for submitting a photograph for the primary voter's guide,[2] Hatfield handily defeated Prince to move on to the general election.[3]

U.S. Congressman Ron Wyden considered challenging Hatfield, but decided against it.[4] Lonsdale, who was unknown as a politician, announced his campaign in March, and came out swinging directly at Hatfield and mostly ignored his primary challengers. Lonsdale's main campaign themes were abortion rights, which Hatfield opposed; and timber management, in which Lonsdale opposed exporting timber from Oregon forests and wanted to restrict logging in old-growth forests.[1] Lonsdale also criticized Hatfield as being out-of-touch with Oregonians after so many years in the Senate. Lonsdale announced that he would refuse to take special-interest contributions in his campaign, and would finance the campaign himself with the millions he had made from Bend Research.[1] Lonsdale easily defeated his competition: Salem attorney Steve Anderson, Pleasant Hill computer programmer Neale S. Hyatt, Milwaukie retired truck driver Brooks Washburne, Eugene activist Bob Reuschlein, and Frank A. Clough, also of Eugene.[1][5][6]

Once the primaries concluded, Hatfield, who had been first elected U.S. Senator in 1966, rolled out his usual campaign honed from his decades of experience: he refused debates, never engaged his opponent directly, and focused on small, friendly campaign appearances that stressed the influence he wielded as a U.S. Senator with seniority and influence.[4]

Lonsdale's self-financed campaign made heavy use of TV attack ads, criticizing Hatfield as being out of step with Oregonians on every issue, but primarily in terms of timber and abortion. He also made use of a nationwide anti-incumbency sentiment, and tore into Hatfield for being too closely tied to Washington special interests, and attempted to tie Hatfield to the Savings and loan crisis of the mid-1980s through his advisor Gerry Frank of the Meier & Frank chain of Oregon department stores, who had ties to a Salem savings and loan.[4] By early October, polls showed the gap closing from 25 down to about 4 points in an early October poll conducted by The Oregonian newspaper, and by the end of October, some polls showed Lonsdale in the lead.[7]

With the polls running against him and time running out, Hatfield, who had not been seriously challenged since first being elected in 1966 and had never lost an election,[8] abandoned his tactic of staying above the fray and not engaging Lonsdale directly. In the media and in television ads, he charged Lonsdale with hypocrisy in his environmental stand, alleging that Lonsdale had allowed his company to illegally dump toxic chemicals into the environment.[9] Lonsdale vigorously denied the charges, which were later shown to have violated no laws, but the tactic may have stalled Lonsdale's momentum.[10] Hatfield went on to win in all but Multnomah, Jackson, Baker, and Lincoln counties to win by more than 7 percentage points statewide.[8]