What Cruz, Sanders need to do after Wisconsin wins

Wisconsin produced the results Ted Cruz and Bernie Sanders have been dreaming of: decisive primary victories over respective front-runners Donald Trump and Hillary Clinton.

Now the question is what each can do with it.

Cruz took a bite out of Trump's delegate lead, winning at least 33 of the 42 delegates at stake in Wisconsin. It was only a modest amount, but every one he takes makes it more difficult for Trump to reach the 1,237 delegates he needs for a first-ballot nomination at the Republican convention this summer in Cleveland.

Bernie Sanders and Ted Cruz
Getty Images (left); Jim Young | Reuters
Bernie Sanders and Ted Cruz

Sanders, because of the proportional rules Democrats use to award delegates, made less progress in narrowing Clinton's large delegate lead. But his solid Wisconsin majority at least gives him a chance to sustain momentum as the race moves toward the Northeast.

The problem facing both leading challengers is that the next contest happens to be the home state of both front-runners.

Clinton remains favored in New York's April 19 primary. A victory in the state that twice elected her to the U.S. Senate would blunt Sanders' momentum argument. And his only remaining chance for the nomination is stringing together a series of solid, lopsided victories that narrow her lead among pledged delegates and generate a collapse in confidence among unpledged "super delegates" who overwhelmingly favor her so far.

At the same time, Republican polls have shown Trump with an enormous lead in New York state, large enough that he can win the vast majority of the 95 Republican delegates at stake. If he can do the same the following week in Maryland, Connecticut, Rhode Island, Pennsylvania and Delaware, he can halt Cruz's momentum and pull close to the delegate majority he needs.

Can Trump get all the way there? At the moment, election forecaster Nate Silver projects the bombastic billionaire ending up 55-to-58 delegates short of a first-ballot victory.

Stay tuned for more primary results.

— Data visualizations by CNBC's John Schoen.