Democratic presidential candidate Hillary Clinton said rival Bernie Sanders would “end all the kinds of health care we know” and criticized his new TV ad in an interview with MSNBC’s Rachel Maddow Thursday night.

And as polls show a much tighter than expected race in Iowa, Clinton questioned whether Sanders’ supporters will actually show up to the state’s caucuses in three weeks. Meanwhile, she said she would be open to an all-female presidential ticket.

The interview will air at 9 p.m. ET, just as the Republican presidential candidates face off in their sixth debate. And it comes just three days before Democrats’ own debate, as Clinton tests out lines of attack she might deploy Sunday night at the debate hosted by NBC.

Clinton’s focus with Maddow, whose fans include many progressive voters, was squarely on her Democratic rival.

Asked about Sanders’ strong support from young people and first-time caucusgoers, which the Des Moines Register compared to the coalition that beat Clinton in 2008 in the state, the former secretary of state said that she has a large base of committed supporters, and questioned whether Sanders’ fans would really turn out on a cold Iowa February night to caucus.

“I have a much better organization than I did back in 2008,” she said. “I have an organization that is a great mixture of people who worked for President Obama in 2008 and 2012, people who worked for me, people new to the process.”

On health care, an issue that has dominated the Democratic primary in recent days, Clinton hoped to convince Democrats that Sanders’ single-payer health care plan is not feasible and warned it would destroy the status quo.

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“It’s a bit concerning to me, because it would basically end all the kinds of health care we know: Medicare, Medicaid, the CHIP program, Children’s health insurance, Tri-care for the National Guard military, Affordable Care Act exchange policies, employer-based policies,” she said. “It would take all that and hand it over to the states.”

It’s a similar charge to the one Chelsea Clinton leveled against Sanders this week, which Politifact rated “Mostly False.”

While Sanders’ plan would replace much of the current health care insurance system, it would not take away any coverage, the fact-checking website found. And contrary to Clinton’s claim that Republican governors could strangle Sanders’ plan, Politifact notes that his plan includes provisions to allow the federal government to take over if states are not cooperating.

Clinton does correctly note that Sanders has so far failed to put out details of his single-payer plan, making it almost impossible to evaluate with much detail or accuracy.

“If you’re going to say ‘free heath care, Medicare for all,’ you owe it to voters to say, this is what it will cost,” Clinton told Maddow. And she added that the Affordable Care Act is one of the greatest accomplishments in the Democratic Party’s history, saying that that it shouldn’t be jeopardized by a divisive push for a single-payer plan.

On a different topic, Clinton took issue with a new Sanders campaign ad released Thursday. “There are two Democratic visions for regulating Wall Street. One says it’s okay to take millions from big banks and then tell them what to do,” Sanders says in the ad, clearly referring to Clinton, though not by name.

Top Clinton officials alleged on a conference call with reporters that the spot violates Sanders’ pledge not to run negative ads. But Maddow wasn’t buying it. “I have seen the ad that you’re referring to. Honestly, it is not much of an attack,” Maddow said.

Clinton pushed back. “What I think people reacted to is that it was a very broad assertion that caught up all Democrats,” Clinton replied. “I mean basically it’s a very direct criticism of President Obama, who, as you might recall, took a lot of money form the financial industry when he ran in 2008. That didn’t stop him from” pushing for Wall Street reform.

“It’s a funny kind of charge. It’s sort of a pox on all your houses for all the Democrats,” she added.

Incidentally, Sanders’ campaign agrees with that interpretation.

Finally, Clinton said she was open to considering a woman to be her vice president, if she gets to make that choice. “I think what’s important is to, you know, really look hard at the talent, the experience, the energy, the commitment, the stamina, you know?” she said. “I’m not ruling anybody out.”

The Democratic front-runner did joke that if she might consider picking Leonardo DiCaprio, fresh off his turn as a frontiersman in “The Revenant,” if she needs a more manly choice.

This story originally appeared on MSNBC.com.