WASHINGTON – Newark, N.J., Mayor Cory Booker took a giant step toward the presidency last Sunday.

On NBC’s “Meet the Press,” Booker called President Obama’s advertisement criticizing Mitt Romney’s tenure at the private-equity firm Bain Capital “nauseating.” His comment has been portrayed as a disagreement with the president over Obama’s ad strategy. What Booker was actually doing, however, was shoring up his base: Bain Capital and all those similarly situated firms that have supported him in the past and will, presumably, do so in the future if he ardently defends them.

“Nauseating” is a word that demands to be heard. Booker could have said “wrong,” “unfair,” “ill-advised.” But he didn’t. And his voice is all the louder directed at the man he is supporting for president.

Aside from describing what Obama’s advertisement is doing to his stomach, Booker said, “We’re getting to a ridiculous point in America.” He added, “It’s either going to be a small campaign about this crap or it’s going to be a big campaign, in my opinion, about the issues that the American public cares about.”

All that said, Booker’s comments might have faded into Sunday talk show obscurity were they not such a clear example of how deeply our politics are controlled by money.

Booker wasn’t committing a Kinsley gaffe, the term for when a politician accidentally tells the truth.

He was purposefully telling the truth. Nary a cent for his campaigns (or revitalizing his city) came from Newark or New Jersey. Most of it came from the mountain of private equity and investment banking just across the Hudson, from which hedge-fund managers and other banking types write big checks to Romney and howl over “class warfare.”

For Obama, this is a lesson in how not to choose a surrogate: Stay away from people still in the game and hoping to run for higher office. No one goes straight from Newark City Hall to the Oval Office.

On his trajectory upward, Booker might enjoy the help of Obama – but he absolutely needs the deep pockets of Wall Street.

Booker could replace Sen. Frank Lautenberg, who is 88 and whose term expires in 2015. Or Booker could run for governor in 2013 against his good friend Chris Christie.

They immortalized their relationship in a video for a New Jersey Press Association Legislative Correspondents dinner. Playing off the Seinfeld-Newman rivalry, they spoof each other with the heroic man of action Booker outdoing the governor at every turn, telling Christie, “I got this” as he changes a flat tire, retrieves Bruce Springsteen’s missing guitar and catches a baby falling from a balcony at the State Capitol. Then at the end Christie grabs the phone from Booker when a call comes from Romney. Smiling, Christie says, “I got this.”

If Booker will diss Obama on “Meet the Press,” he certainly won’t shy from wiping that smile off Christie’s face – a move that will be expensive. To do that, Booker will need Wall Street, and he has seen what can happen to you when you don’t bow to the 1 percent.

For nothing, really, Obama lost their love. He neglected to thank them for treating the economy like a casino, nearly destroying it. Later he mildly criticized them for awarding themselves outsized bonuses after being rescued by the U.S. taxpayer, once referring to them as “fat cats.” Compare this to FDR saying he welcomed the hatred of the banks or JFK facing down “a tiny handful of steel executives whose pursuit of private power and profit exceeds their sense of public responsibility.”

If anything, Obama hasn’t done enough to close down the casino. The regulation in the Dodd-Frank financial reform law has been so watered down at the behest of lobbyists that JPMorgan Chase’s chief executive officer, Jamie Dimon, drove a Brinks truck through the loopholes.

His $2 billion-plus gambling loss is not enough to require help from the Treasury – yet.

Lose a few billion more, however, and he might.

It all adds up to one more example of how the rich are different from you and me: They have very thin skins. Obama’s take from Wall Street groups that gave him record amounts of cash in 2008 is way down. Booker can’t afford that.

Still, Booker had to retreat a little or look as if he was openly courting the rich guy at the expense of the little one. (You’re supposed to woo the rich guy in private.)

So Booker made a video to “expand on his support for President Obama,” which has everything but a newspaper held up to verify that the hostage is still alive.

In one of those clarifying statements perfected by politicians, in which he seemed to be reading off a script on his open laptop, Booker explained that when he used the word “nauseating,” he was referring to how he feels when he sees “people in my city struggling with real issues.”

Real or not, this political tiff pushed aside wars and the European financial collapse at Obama’s news conference at the NATO summit in Chicago. Obama reformulated his argument for Booker and any other Democrat who might choose Wall Street over Pennsylvania Avenue: “If your main argument for how to grow the economy is, ‘I knew how to make a lot of money for investors,’ then you’re missing what this job is about.”

In fairness to Booker, Democrats have a harder time than Republicans when it comes to raising money from the rich. Republicans are expected to do the wealthy’s bidding, so they need not be apologetic. Democrats are supposed to be looking out for the little guy, so we are naturally suspicious when they take meals in the privacy of Park Avenue.

It brings to mind the wisdom of Jesse Unruh, former speaker of the California Assembly: “If you can’t drink a lobbyist’s whiskey, take his money, sleep with his women and still vote against him in the morning, you don’t belong in politics.”

As he enters the expensive world of a statewide race, Booker can live without a friend (the president) – but not without a multimillionaire or two.

Undoubtedly he’s betting the private-equity guys will remember the first video, and everyone else the second.