"Secretary Clinton appears to be getting a little bit nervous," he told a crowd in Philadelphiaon yesterday. "And she has been saying lately that she thinks that I am 'not qualified' to be president. Well, let me, let me just say in response to Secretary Clinton: I don't believe that she is qualified.''

Sanders beat Clinton with 54 percent to 46 percent on Tuesday during the Wisconsin presidential primary on Tuesday.

The win in Wisconsin will also allows Sanders to make the case to 'super-delegates', who can make up their minds about whom to support.

After Wisconsin, the next state to vote in the primaries to elect the Republican and Democratic candidates for the November presidential election is New York, where voters will go the polls on April 19.

The two candidates will face off in a debate in New York on April 14, hosted by TV channels CNN and NY1.

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