WASHINGTON President Donald Trump s choice to manage the federal governments budget admitted Tuesday that Social Security is in fact constitutional, but he was still not willing to renounce his description of the program as a Ponzi scheme.

Rep. Mick Mulvaney (R-S.C.), the nominee to head the Office of Management and Budget, also refused to say at his confirmation hearing whether hed push Trump to keep his campaign pledges to not cut Medicare, Medicaid and Social Security.

The OMB is in charge of making sure the government is running properly and crafting the administrations budgets.

Since Trump had said repeatedly on the campaign trail that he would not touch benefits in the key social safety net programs, Democrats on the Senate Budget Committee were curious to know whether Mulvaney would seek to push his own views at the OMB or would work to implement Trumps promises.

Sen. Bernie Sanders (I-Vt.), who serves as the ranking minority member on the committee, reminded the nominee that as a member of the South Carolina legislature, he had been one of just six lawmakers to vote for a bill that declared Medicaid and Social Security unconstitutional.

Mulvaney said he didnt remember that, but said he would not carry that view into the White House.

I will not be arguing to the president of the United States that Social Security or Medicare are unconstitutional, Mulvaney said.

He did not, however, renounce his past declarations that Social Security is a Ponzi scheme when Sen. Debbie Stabenow (D-Mich.) gave him the chance.

I wouldnt read too much into the description of it as a Ponzi scheme. Its simply describing to people how the cash flows, Mulvaney said. He said his earlier remarks merely refer to the fact that fewer workers are now supporting each Social Security recipient than in the past, which he argues means that eventually some people will be left holding the bag.

The broader point that Sanders and Stabenow were pushing was the question of whether they could trust Mulvaney to help Trump pursue his campaign pledges on entitlements, which Democrats support.

We have a president who ran on a set of principles that he would not cut Social Security and Medicare and Medicaid, yet he is nominating someone whose views are very, very different. I have a real problem with that, Sanders said. He asked Mulvaney if hed help Trump keep his word or try to sway him in Mulvaneys direction.

The congressman suggested hed push for his own views.

The only thing I know to do is to tell the president the truth, Mulvaney said. The truth is that if we do not reform these programs that are so important to your constituents in Vermont and to mine in South Carolina, I believe in nine or 10 years the Medicaid trust fund is empty, and roughly 17 or 18 years, the Social Security trust fund is empty.

Mulvaney told other senators that he would back means testing and raising the retirement age as some of the ways to fix the problems.

Sanders doesnt dispute that changes need to be made to the safety net programs, but he was not reassured by Mulvaneys comments.

The problem that Im having right now is not just your nomination, but the integrity and honesty of somebody who ran for office on one set of principles nominating somebody else whose views are very different, Sanders said.

How will Trumps first 100 days impact you? Sign up for our weekly newsletter and get breaking updates on Trumps presidency by messaging us here .