Hillary Clinton. Spencer Platt/Getty Images Hillary Clinton on Wednesday leveled a new line of attack against Bernie Sanders: He doesn't have the in-depth policy knowledge to be president.

The Democratic presidential frontrunner's campaign hosted a conference call to highlight the differences between the two candidates on gun policy, in particular.

During the call, two Connecticut lawmakers said that Sanders "did not understand" the effects of the 2005 Protection of Lawful Commerce in Arms Act, which protects gun manufacturers from most lawsuits from families of victims of gun violence.

"I think he's wrong, and I think it speaks to his not understanding the importance of this issue, and not understanding the responsibility of leadership," Rep. Elizabeth Etsy said of Sanders' stated position on the issue.

"Sen. Sanders either doesn't understand the law that he claims to support, or he no longer supports it," argued Sen. Chris Murphy.

Both lawmakers represent Newtown, Connecticut, which was the site of the 2012 Sandy Hook Elementary School mass shooting.

Former New York Rep. Carolyn McCarthy, whose husband died in a mass shooting, was even more blunt. McCarthy said on the call that Sanders is "not ready to be president of the United States."

"I feel that with my heart and soul," she said.

The Clinton campaign call came two days after the Daily News published the transcript of a wide-ranging Sanders interview in which the senator appeared to fumble a number of the questions.

Sanders dodged questions on foreign-policy topics, stood by his support for gun manufacturers in certain cases, and appeared flustered by probing inquiries into his plan to break up major financial institutions. But some people defended Sanders by arguing that the tabloid's editorial board botched its questions.

Clinton's campaign wasted little time promoting the interview throughout the day on Tuesday. Her team emailed reporters and supporters the entire transcript. Later, her communications staff sent reporters a list of stories criticizing Sanders as out of his depth on policy issues.

Hillary Clinton. AP Photo/Matt Rourke

On Wednesday, Clinton also questioned Sanders' preparedness for office.

In an interview on MSNBC's "Morning Joe," Clinton said that Sanders was not prepared to answer policy questions in key areas, a sentiment she echoed later in front of a Pennsylvania union audience.

"I think he hadn't done his homework and he'd been talking for more than a year about doing things that he obviously hadn't really studied or understood," Clinton said on MSNBC, "and that does raise a lot of questions."

She continued: "Really what it goes to is for voters to ask themselves: Can he deliver what he is talking about? Can he really help people? Can he help our economy? Can he keep our country strong?"

During another Wednesday interview, Clinton said on CNN that she was surprised by Sanders' apparent stumble on his plans to break up major banks using authority granted under the Dodd-Frank Act.

"In the interview, it seemed unclear that he knew how Dodd-Frank worked. I think I, and many other people were surprised, because that's been the centerpiece of his campaign for months," Clinton said.

The sparring comes as the Clinton campaign is reportedly shifting its strategy to attack Sanders in public with full force before the New York primary in two weeks.