Should Republicans let history (and Ohio?) be their guide?

Ted Cruz's decisive victory in Wisconsin over Donald Trump now makes the possibility of a contested convention, once dismissed as remote by many commentators (myself included), ever more likely.
To clinch the Republican nomination, a candidate must obtain a majority of delegates to the Republican National Convention, the magic 1,237. In order to win outright, Trump now needs 55 percent of the remaining delegates in up coming contests.