Story highlights The critique was a step further than she usually goes on the subject

Sanders listed the Democratic Party as his party affiliation in his statement of candidacy

Philadelphia (CNN) Hillary Clinton stepped up her criticism of Bernie Sanders following his victory in the Wisconsin primary Tuesday, questioning the Vermont senator's fidelity to the Democratic Party and knocking him for his inability to answer questions in an interview with the New York Daily News.

"He's a relatively new Democrat, and, in fact, I'm not even sure he is one," Clinton told Politico's Glenn Thrush in an interview published on Wednesday morning . "He's running as one. So I don't know quite how to characterize him. I'll leave that to him."

The critique was a step further than she usually goes on the subject, which she typically brings up to tout her own long history with the party.

Clinton continued that line of attack on MSNBC's "Morning Joe" Wednesday morning.

Asked if she thinks Sanders is a Democrat, Clinton replied, "I think he himself doesn't consider himself to be a Democrat."

Read More