A campaign adviser for Senator Bernie Sanders (I., Vt.) hit Senator Kamala Harris (D., Calif.) for saying she could pay for her health care plan without raising taxes on the middle class.

When asked if it would be possible to have a Medicare for All plan without raising taxes on the middle class, Sanders senior adviser Jeff Weaver told MSNBC's Hallie Jackson that it would not be possible "without unicorns, magic wands," adding, "Healthcare is not free. There's doctors, nurses that have to be paid. There's hospitals. You have to pay for it."

When Jackson asked if Harris's plan was unrealistic, Weaver said, "I do not know how you fund healthcare for everybody in America without paying for it. You have to pay for it."

Harris has faced questions about whether she would raise taxes on the middle class to pay for her Medicare for All plan. She told CNN's Kyung Lah "Part of it is going to be about Wall Street paying more. It's going to be about what we tax in terms of financial services. That's part of it. The other part is to ups understand this is about an investment that will reap a great return on the investment."

When pressed on whether Wall Street could cover the estimated $30 trillion price tag over ten years, Harris avoided the question, saying, "What we're doing right now is unaffordable to so many American families. And the idea that we're going to go down and this level of analysis that suggests that status quo is okay is completely unacceptable."

Sanders has said he would raise taxes to cover his Medicare for All plan, most prominently in the Democratic debate. Harris said her healthcare plan was similar to Sanders's, and that she supported his Senate bill.