Republican Gordon Smith is falling farther behind, according to the latest DailyKos/Research 2000 poll. Conducted 10/14-15, the poll surveyed 600 likely voters for a margin of error of +/- 4%. Smith and Democrat Jeff Merkley were tested.

General Election Matchup
(All / Dem / GOP / Ind / Men / Wom)
Merkley...47 / 81 / 6 / 45 / 44 / 50 (+2 from last, 9/24)
Smith.....41 / 6 / 83 / 41 / 44 / 38 (+1)

Obama.....53 / 85 / 15 / 53 / 51 / 55
McCain....38 / 7 / 78 / 35 / 42 / 34

Smith has a net-unfavorable rating, 40% favorable to 47% unfavorable, and it's looking increasingly like the incumbent senator will face an uphill climb to keep his seat.