Research 2000 for Daily Kos (8/31-9/2, likely voters):
Harry Reid (D-inc): 40
Danny Tarkanian (R): 45
Harry Reid (D-inc): 41
Susan Lowden (R): 44
(MoE: ±4%)
These results match pretty well with recent internal surveys released by the camps of Lowden and Tarkanian, and also with Mason-Dixon's latest survey of the state.
Now, some may say that Reid has a lot of room to grow due to his early inability to consolidate the Democratic vote (just 70% of Dem voters are committing themselves to his re-election so far, compared to over 80% of Republicans who are firmly voting against him), but I'd still call this "deep shit" territory. Reid's going to be draining his war chest dry -- and probably lean on the DSCC to help -- even if the GOP nominates a third-stringer like Tarkanian or Lowden. Even if Reid manages to survive, it looks like it'll be an ugly win.