The Trump administration's proposed budget won't last long, one expert told CNBC on Tuesday.
"The accounting in this budget is really just crazier than I've ever seen," he added.
President Donald Trump's proposed fiscal 2018 budget became public Monday night. It looks to cut federal spending by $3.6 trillion over the next decade, slashing funding to many agencies and programs, including Medicaid.
"We shouldn't be constrained by pessimism — but we should be constrained by arithmetic," Bernstein added, responding to an earlier statement by Office of Management and Budget Director Mick Mulvaney.
"That assumes a pessimism about America, about the economy, about the people, about its culture that we're simply refusing to accept," Mulvaney said Monday. "We do not believe that [3 percent] is something fanciful."
The proposed budget expects the economic growth rate to rise to 3 percent, higher than the 1.9 percent growth forecast by the Congressional Budget Office.
Bernstein added that he is concerned about some of the budget's similarities to others proposed in the past by House Speaker Paul Ryan when Republicans did not have a majority in Congress.
Watch: Hoyer says WH budget 'not a real document'