There are a linty of reasons why you cannot just divide the probability of victory in the general election by the probability of victory in the primary and get the conditional probability of candidate winning the general elections on their nomination. First, these values are both imprecise. Second, things change conditional on nomination (i.e., there is a complicated relationship between these two estimates). Third, candidates do not technically need to be the party nominee to win the general (although it is nearly 0% that any candidate wins the general should they not be a major party nominee). I could go on, but this simple rubric is suggestive of something.

The markets have been extremely consistent that Donald Trump is more likely to win the general, conditional on getting the nomination, than Ted Cruz. (The missing data in the late February is when Cruz dropped below 5% to get the nomination.)

PredictWise20160424a