The Republican budget dilemma, in one video

There's a lot packed into this 46-second clip of Rep. Mick Mulvaney, the conservative Republican nominated to run Trump's OMB, being confronted over Trump's promise to balance the budget while cutting taxes and refusing to cut entitlements. It neatly summarizes the fiscal clash that seems inevitable between the White House and the Hill.

The key exchange:

Corker: "Mr. Trump did say some things during the campaign that I wish he had not said. They're totally unrealistic, make no sense whatsoever. And I just wonder if your sense that when you talk with him about the five levers and when you talk with him about the fact that it's impossible for us to balance the budget with 31% of our spending being discretionary without dealing with these other programs, do you think he understands that?"

Mulvaney: "I have to imagine the President knew what he was getting when he asked me to fill this role."

Corker: "So you think he understands that we have to deal with all of these issues?"

Mulvaney: "I'd like to think it's why he hired me."

Why this matters: Trump's pledges don't add up — a fact colorfully acknowledged by the staunch Trump ally, Tennessee Sen. Bob Corker. Mulvaney, one of the chief fiscal hawks in the House, knows this all too well, and his relationship with Trump could prove contentious if the President favors deficit spending.