President Trump's Budget Director Mick Mulvaney spoke with CNBC's John Harwood about what to expect from the administration's four-year economic plan — and he's more realistic about what is and isn't possible.

Our thought bubble: Mulvaney is known as a deficit hawk, but he says he's planning to work within the constraints the president has set out (no entitlement cuts, infrastructure and military spending on the rise), so it won't be easy to cut spending and eliminate the debt to the degree he might otherwise like.

Trump's trillion dollar infrastructure plan is "the most efficient way to actually allocate resources," Mulvaney argued, adding, "It's a little less important to me if infrastructure adds to the deficit."

On the debt ceiling: "Yeah, we're going to raise the debt ceiling. But we're going to have to do it as part and parcel of a larger thing."

An impending government shutdown: Mulvaney told Hardwood the chances of a shutdown are "very low" and insisted that it wouldn't be that big of a deal because "83% of the government stays open in a government shut-down. Social Security checks go out, military still exists. ...I think the consequences have been blown out of proportion."