Among corporate America's biggest worries about a Biden presidency was that he might cave to the left wing of his party and select Elizabeth Warren as his top white-collar-crime cop.

Well, the corporate chieftains dodged that bullet, only to find themselves now in the crosshairs of the next worst thing.

To say Gary Gensler — nominated as head of the Securities and Exchange Commission — is the favorite regulator of the business-hating Massachusetts senator isn't an overstatement. Both he and Warren view the business of monitoring securities markets and regulating big business as more of a progressive holy war than matter of governance.

With that you can expect not just the usual flurry of enforcement activity out of the agency when Gensler comes to town. People who know Gensler tell me he is also intent on remaking the SEC in Warren's image.

"Wall Street's top cop" could soon become the left's enforcer of social-justice and other progressive causes on big business if Gensler has his way, these people say.

Warren became a hardened anti-business radical after years in academia. She is most famous for her annoying anti-bank rants in the Senate, and before that creating the Consumer Financial Protection Bureau, a watchdog that has very little substance on its résumé to show it helps consumers. (It famously missed the Wells Fargo fake-account scandal, which was uncovered by journalists).

Gensler's sharp left turn has been more circuitous. He worked nearly two decades on Wall Street, at the much-maligned Goldman Sachs, no less, doing stuff that would make Warren's skin crawl: earning millions of dollars helping companies merge and acquire one another.

At one point he was the youngest person to be made partner at the firm — joining a rarified club at Goldman that puts you in line to make even more money.

In other words, Gensler had fat cat written all over him, until he went into government and his radicalization began, I am told by people who worked with him. Gensler served under Treasury secretaries Bob Rubin and Larry Summers during the Clinton years, and "when he first got there it was like dealing with a banker," said one prominent attorney who reps banks before government agencies and spoke on condition of anonymity.

"He was completely reasonable," the lawyer continued, "but over time you can see him changing, becoming more progressive and left-leaning in policy and temperament."

Gensler didn't return emails seeking comment, but based on accounts from people who worked with him, his progressivism truly began to manifest itself when he left the Clinton White House and joined the staff of Democratic Sen. Paul Sarbanes.

There he helped Sarbanes craft the ill-conceived Sarbanes-Oxley reform act that was supposed to stop corporate crimes after the Enron scandal but failed to rein in the biggest flaws in the financial system that led to the 2008 financial crisis.

That collapse and the Obama administration's response to it — more heavy-handed regulation — gave Gensler another shot at reining in corporate abuse as head of the Commodity Futures Trading Commission.

The seemingly arcane-sounding agency is among the most powerful regulators of banks since it monitors the massive futures and derivative markets. It is there where Gensler fully earned his rep as Warren's favorite former fat cat.

He embraced the role of regulator of a market that had little real responsibility for the 2008 crisis with a zeal that would lead you to think all those subprime loans that blew up the financial system were a function of futures trading.

Then came his crusade against banks for manipulating the London InterBank Offered Rate (Libor), an important interest rate on loans mainly between banks but also used in setting rates on mortgages and other loans. Here he was very "successful" — squeezing billions of dollars out of banks in settlements even if many of the alleged manipulations were legally dubious.

For all the headlines this scandal produced, many of the traders charged were eventually acquitted, particularly after evidence emerged that the manipulation was done often at the behest of central bankers looking to lower rates during the height of the financial crisis.

Like any good progressive, Gensler got his card punched in academia. After leaving the Obama administration he became a professor at MIT, teaching and conducting "research . . . on blockchain technology, digital currencies, financial technology and public policy," according to his biography.

Gensler's academic interest in blockchain and technology, I am told, provides clues on some of his regulatory priorities. He is said to be interested in abuses involving cryptocurrencies and fintech — or Wall Street's embrace of computer technology.

He will also delve into more opaque areas of the securities markets such as Special Purpose Acquisition Companies (SPACs), which provide a low-cost method of taking companies public without relying on the traditional IPO process.

All of which is warranted to some degree. But the biggest change Gensler will likely bring to an agency designed to make sure average people can buy stocks without getting ripped off will be cultural. He will be looking for ways to make companies adhere to various left-leaning edicts involving diversity, climate change and even making it difficult for corporations to make political contributions.

The last edict is something Warren has been pushing for years, though she did not expand it to progressive power players like unions.

Luckily for the business community, Warren was rebuffed by ­Obama SEC chief Mary Jo White, who believed such moves are far outside the SEC's mandate.

In Gensler, Corporate America's luck just ran out.