dems need 4 on an HRC win. Il, IN, and WI make 3. They need NV only -OR- any two others if they lose NV (as that would be a flip, Reid's seat) the two others would draw from most likely PA, NH, MO, NC.
GOP leads NV, but it is polled thinly, polls poorly (Reid was supposed to lose for sure last time).
PA is a straight ticket state, a GOP turnout collapse could hurt Toomey. Its the only straight ticket state in the close ones.