Jim Slattery (D): 36
Pat Roberts (R-inc): 48
That twelve point margin is a constant in every poll of this race that we've seen so far (Rasmussen in May and Research 2000 last week), so I think we can believe these numbers.
With only 56% name recognition, Slattery does have some room to grow, and Roberts' numbers are decidedly mediocre: a 47/43 job performance rating and a 48/29 favorability score. Even more startling is the generic Senate ballot, where the GOP is basically tied with the Democrats at 41-40. The numbers certainly suggest that while this is an uphill fight, Slattery has something to work with.
In the presidential race, the poll finds Obama trailing McCain by an eye-popping 45-41 margin in the state. In 2004, Bush smacked Kerry by 62-37 here.