Editor’s Note: Paul Begala, a Democratic strategist and CNN political commentator, was a political consultant for Bill Clinton’s presidential campaign in 1992 and served as a counselor to Clinton in the White House. The opinions expressed in this commentary are his. View more opinion articles on CNN.

CNN  — 

There is a bit of a brother-and-sisterhood former senior White House aides. Despite deep political and policy differences, I respect those who choose to serve. The White House can be a dream job – it was the best professional experience and highest honor of my life. But it can also be, as President Clinton told me the first time I set foot in the Oval Office, “the crown jewel of the federal penal system.”

My heart usually goes out to White House staffers. The hours are long, the challenges great. So it is with no joy that I offer this assessment of Mick Mulvaney’s performance running Donald Trump’s White House: it stinks.

Acting White House chief of staff Mulvaney needs to start acting like a chief of staff.

In his press briefing today, Mulvaney revealed himself to be a yes-man when this President needs someone who can tell him no.

The most important, most difficult, most loyal two words a White House staffer can use are: “No, sir.”

President Trump is on his third chief of staff and diminishes and insults Mr. Mulvaney by making him merely “Acting” chief of staff. He’s on his fourth national security adviser, his third press secretary, and his third defense secretary. Trump burns through people, it seems, until he gets what he wants. What’s more important is what he needs – what we all need. And that is a White House staff that will tell him to knock it off.

When the President wants to politicize national security, corrupting it for his partisan needs, the only acceptable response is “No, sir.” When he seeks to take Ukraine policy away from Ukraine policymakers and give it to his unappointed, unconfirmed, unaccountable private lawyer, Rudy Giuliani, the only acceptable response is “No, sir.” When the President acts as if he is above the law and beyond the Constitution, directing a global summit and millions of dollars to one of his golf resorts, the only acceptable response is “No, sir.”

Instead, Mr. Mulvaney debases himself. When ABC’s Jonathan Karl asked him about the clear quid pro quo in Mr. Trump’s dealings with Ukraine, Mulvaney sniffed, “We do that all the time with foreign policy.” That’s the problem, Mick. The Corleone family used extortion all the time, too. Didn’t make it right. Mulvaney was even more dismissive of those who decry political desires overruling security interests: “Get over it.”

He was just getting started. Mr. Mulvaney, defending the indefensible grift of President Trump ordering that the G-7 summit be at his Trump National resort in Doral, Florida, laughably claimed of Mr. Trump, “He’s not making money off of this.”

Baloney. Trump’s decision will flood his resort with federal funds for security, communications, and a host of other needs. Advance teams from around the world will fill the resorts’ rooms for weeks, maybe months. Foreign governments will spend huge sums – generating profits that will line Trump’s pockets.

This is precisely what the Constitution forbids in Article I, Section 9, when it states that no one occupying federal office can accept an emolument – which is profit – from a “King, Prince or foreign State.” (Incidentally, Pulitzer Prize-winning investigative journalist David Fahrenthold, of the Washington Post, has reported that revenue at Trump’s Doral resort fell 13.8% from 2016 to 2017, and net operating income fell 62%.)

No sir. That’s what you say. No sir, you can’t shake down Ukraine for dirt on Joe Biden. No, sir, you can’t withhold military aid if the Ukrainians don’t embrace a nitty right-wing conspiracy theory. No, sir, you can’t call on China to interfere in our elections the way you called on Russia to. No sir, you can’t spend millions of taxpayer dollars at your own resort. No sir, you can’t reap profits from foreign governments spending millions at your resort either. No sir, you’re not above the law.

Those words never seem to emerge from Mr. Mulvaney’s mouth. Far from being a public servant, the acting chief of staff revealed himself to be a throne-sniffer of the worst order. If he were any more of a toady, he’d be catching flies with his tongue.