Marquette is the best pollster when it comes to Wisconsin, but unless they find Burke with a larger lead or other pollsters (PPP, Quinnipac, SUSA) find Burke up, still tilt/lean R.
Every single poll since April has shown either a 1 point Walker lead, a tie, or 1 point Burke lead. This race is the definition of toss up. To call it "lean R" is completely nonsensical.
It's Lean R in my opinion because Walker won in a recall election. It's not crazy to think he'll win a General Election.
It's not crazy to think he'll win. It's crazy to think he has a strong advantage since all evidence points to the contrary. Barrett was a weak candidate, and the exit poll overwhelmingly showed that voters thought recalls should only be used for official misconduct, not because people disliked their policies. That padded Walker's margin as well.
Lean R =/= a strong advantage. It means he's a slight favorite.