Oregon Democratic primary elections, 2008 Polling Major

| Source_ | Date_ | Clinton | Obama | Undecided |
|---|---|---|---|---|
| SurveyUSA | May 16–May 18, 2008 | 42% | 55% | 1% |
| Suffolk | May 15–May 17, 2008 | 41% | 45% | 8% |
| American Research Group | May 14–May 15, 2008 | 45% | 50% | 5% |
| Public Policy Polling (D) | May 10–May 11, 2008 | 39% | 53% | 7% |
| SurveyUSA | May 9–May 11, 2008 | 43% | 54% | 2% |
| Davis, Hibbitts & Midghall | May 8–May 10, 2008 | 35% | 55% | 10% |
| Rasmussen Reports | May 1, 2008 | 39% | 51% | 10% |
| SurveyUSA | April 28–April 30, 2008 | 44% | 50% | 4% |
| SurveyUSA | April 4–April 6, 2008 | 42% | 52% | 3% |
| Riley Research Poll | January 21–January 29, 2008 | 36% | 28% | 13% |