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In Wisconsin, anti-Trump outside groups spent $2 million in ads -- which helped defeat the real-estate mogul in that state a week ago.

But in New York, where Donald Trump is leading his Republican rivals by more than 30 points, these same anti-Trump groups haven't spent a single cent, according to ad-spending data from SMG Delta.

Indeed, the only Republican who has spent money so far in ads for the April 19 contest is John Kasich -- at just $177,000.

The biggest overall spender in New York is Democrat Bernie Sanders, whose campaign has aired $2.3 million in ads, versus $1.2 million for Hillary Clinton.