With 66 percent of the votes counted, Obama led Republican challenger Mitt Romney with 54 percent of the vote to 44 percent.
Rep. Greg Walden, R-Ore., was the only GOP House candidate to prevail Tuesday. Walden, who was first elected to Congress in 1998, trounced Democrat Joyce Segers in District 2. With 59 percent of the votes counted, Walden had 69 percent to Segers' 29 percent.
Measure 80 legalizing marijuana appeared headed for defeat with 52 percent of the votes tallied. The proposal, which had fallen short in pre-election polls, trailed by 10 percentage points late Tuesday.
Oregon legalized medical marijuana in 1998. Measure 80 would have eased controls further and placed pot on a regulatory level comparable to alcoholic beverages.