Matched up against Trump and Cruz, both Clinton and Sanders lead by as much as 14 points, as is the case of Sanders' lead in a hypothetical race with Trump. On the other hand, Kasich outperformed both Democrats when tested head-to-head, leading Clinton 47 percent to 39 percent and Sanders 45 percent to 44 percent.Based on that, vote Kasich.
Polls of hypotheticals mean little to nothing, even at this late date - many voters act differently when given the ballot.