Vermont Sen. Bernie SandersBernie SandersSanders dodges question on FBI investigation into his wife Major progressive group rolls out first incumbent House endorsement A bipartisan consensus against 'big pharma' is growing in Congress MORE may have provided Hillary ClintonHillary Rodham ClintonAmazon’s acquisition of Whole Foods underscores the threat posed by ‘big data’ Pro-Trump group blasts 'rigged' Russia probe in ad starring Tomi Lahren Trump believes Russia 'probably' behind election hacking MORE with campaign advertisement fodder at Monday night’s Democratic presidential forum in Iowa, acknowledging that his healthcare plan will require raising taxes.

Sanders was pressed on the specifics of his Medicare For All healthcare plan, which he has said will require a tax hike but which he claims will save individuals money overall by eliminating private healthcare premiums.

“We will raise taxes, yes we will,” Sanders declared, calling criticim of his plan “disingenuous.”

But Clinton allies were already taking to Twitter to hammer Sanders for the remarks.

The Clinton campaign has accused Sanders of seeking to dismantle ObamaCare to implement a single-payer system, warning that he risks giving away gains liberals have made under the Affordable Care Act.

Some have questioned that line of attack; the single-payer system is popular among liberal primary voters.