Official GRE Verbal Guide TC doubt

Please help in cracking the logic of this problem.

Apply Math Strategy :
{Not (-ve)________} Nevertheless = contrast { Governor throw(veto) the proposal }

After the dividing word (nevertheless) we have a negative idea and as the dividing word is a contrast , so, Idea before the dividing word should be positive but there is a caveat due to the not before the blank we need to fill the blank with a negative work to make the overall idea positive.

From this idea before nevertheless has to positive thus, blank should be a negative.

Only negative word in the answer choice is E

Thankyou @HoldMyBeer