Hillary Clinton, stung by a string of losses, is testing a new line of attack against rival Bernie Sanders ahead of New York's Democratic primary: sharply questioning his credentials and suggesting he lacks expertise to implement his campaign pledge to break up big banks.

Meanwhile, a Super PAC, an outside funding group, supporting Clinton's presidential bid, has circulated comparisons between Sanders and divisive Republican front-runner Donald Trump.

The two-pronged attack, ahead of New York’s nominating contests on April 19, focused on Sanders' wide-ranging and policy-heavy interview with the New York Daily News.

RELATED: If Bernie Sanders were a woman, he'd be unelectable

The Super PAC, Correct the Record, circulated a mash-up of television pundits criticizing Sanders’ perceived missteps in the interview, quoting one calling it “almost Trumpian.”

In an email to supporters, a senior Clinton campaign aide said “even on his signature issue of breaking up the banks” Sanders had been “unable to answer basic questions.” The email included a transcript of the full interview.

“If you are going to be a single-issue candidate, at least know your single issue,” Clinton campaign spokesman Brian Fallon said on Twitter.

“After reading the NYDN interview today, I feel like someone should ask HOW after every one of these declarative sentences in Sanders stump,” spokesman Jesse Ferguson posted Tuesday on Twitter.

Sanders has made reducing income inequality and breaking up “too-big-to-fail” banks central to his presidential campaign, blasting Clinton for money she received for speeches to banks and accusing her of being too closely tied to the financial industry.

The escalating tension between the two candidates, who for months refrained from criticizing one another outright, comes after Sanders took Wisconsin on Tuesday to notch six of the last seven contests for the Democratic nomination.

Sanders continues to trail Clinton in the pledged delegates they need to win the nomination ahead of the party’s July convention in Philadelphia.

Clinton sees New York, a state that she represented as a U.S. senator for eight years, as home turf.

RELATED: Photos: Phish drummer stumps for Bernie Sanders in Philly

Sanders, now a U.S. senator from Vermont, has reminded voters he was born and raised in New York.

Clinton's campaign headquarters is there.

“Look, I think I know the state a lot better. I have a lot of recent experience,” Clinton told CNN on Wednesday.

In the same interview, Clinton said she was “appalled” by statements Sanders made to the New York Daily News about gun manufacturer liability and said it was “unclear as to whether he understood how Dodd-Frank works,” referencing a Wall Street reform law.