President Trump’s pick to be the next U.S. attorney for the Southern District of New York, Jay Clayton, is the chairman of the Securities and Exchange Commission and a longtime corporate lawyer with deep connections to Wall Street. But he has no experience as a federal prosecutor.

After three years at the SEC, Clayton was widely expected to step down this year and return to New York where he had spent decades as a top corporate lawyer.

Instead, Clayton has been thrust into a battle over leadership of the Southern District of New York.

U.S. Attorney General William P. Barr announced Friday night that Trump intends to nominate Clayton to replace Manhattan U.S. Attorney Geoffrey Berman, who has overseen a number of investigations involving the president and his political campaign. But a few hours later, Berman said he was not resigning, and Saturday morning showed up to work.

The battle for control of the office escalated Saturday when Barr said Trump had fired Berman. “As we discussed, I want the opportunity to choose a distinguished New York lawyer, Jay Clayton, to nominate as United States Attorney,” Barr said in a letter to Berman. Berman then announced he would step down immediately.

One Justice Department official, speaking on the condition of anonymity due to the situation’s volatility, told The Post that the change arose because Clayton was preparing to leave the SEC and had expressed interest in the New York prosecutor job.

Clayton is facing an uphill battle to win Senate confirmation. Senate Minority Leader Charles E. Schumer (D-N.Y.) has already called on Clayton to drop out. “Jay Clayton can allow himself to be used in the brazen Trump-Barr scheme to interfere in investigations by the U.S. Attorney for SDNY, or he can stand up to this corruption, withdraw his name from consideration, and save his own reputation from overnight ruin,” Schumer said on Twitter.

Schumer also called on the Justice Department’s inspector general as well as its office of professional responsibility to investigate why Trump and Barr dismissed Berman.

Meanwhile, Senate Judiciary Committee Chairman Lindsey O. Graham (R-S.C.) said Saturday that he would not move forward on confirmation hearings for Clayton unless the appointment is supported by New York’s two U.S. senators, Schumer and Sen. Kirsten Gillibrand (D-N.Y.).

Democrats have also long been skeptical of Clayton’s close ties to Wall Street.

Before Trump nominated him to the SEC, Clayton, a longtime partner with Sullivan & Cromwell, had never held a government position. He has represented some of the biggest names in the financial world, including Goldman Sachs and Bill Ackman of Pershing Capital.

On his 2017 SEC financial disclosure form, for example, Clayton listed Deutsche Bank as a source of compensation “exceeding $5,000.” The bank was a client of his former law firm Sullivan & Cromwell.

The German bank has repeatedly run afoul of federal and state authorities and been caught up in large money laundering schemes. It is also at the center of a battle between the Trump administration and House Democrats over the release of the president’s financial records. The bank has played a critical role in Trump’s real estate business, lending him more than $360 million since 2012.

When he took the job at the SEC in 2017, Clayton agreed to recuse himself from cases involving Deutsche Bank and other clients he had previously represented for two years. While at Sullivan & Cromwell, he advised Goldman Sachs and Barclays Capital, among many others.

Since taking control of the agency, Clayton has often talked of wanting to focus attention on protecting retail investors and drawn praise for tackling complex market issues. The agency also cracked down on cryptocurrency scams, filing numerous cases over the last few years.

Among the most high-profile enforcement actions under Clayton’s leadership was SEC’s $20 million settlement with Tesla CEO Elon Musk, who was accused of misleading investors. The SEC and Musk ended up in court after the agency accused the billionaire of violating the terms of the deal.

“I think that Jay Clayton has done a good job of running the agency and making the trains run on time,” said James Angel, associate professor at Georgetown University’s McDonough School of Business, who has studied markets and financial exchanges. “Most of what has been done during his chairmanship has been technical stuff that was needed.”

But consumer advocates say some of the SEC policies under his leadership could hurt consumers in the long run, including allowing more companies to raise money without traditional oversight. They have been particularly critical of a rule requiring brokers not put their own interests before those of their clients, which they say is too weak.

Clayton’s tenure will be known for “shrinking both the scope and the effectiveness of SEC regulation,” said Marcus Stanley, policy director at Americans for Financial Reform, an advocacy group.

Clayton said in a note to SEC employees just after midnight on Saturday that he will stay “fully committed” to his current job as SEC chairman until being confirmed. “It is a great honor to be considered for this position,” Clayton said.

If confirmed, Clayton, who has never been a federal prosecutor, will need to surround himself with seasoned professionals and leverage his experience at the SEC, Jacob S. Frenkel, a former senior counsel in the SEC’s enforcement division, said in an email. “The US Attorney sets policy and enforcement priorities; he is not in the courtroom,” he said.

He now has three full years making decisions about whom to charge and for what conduct in a civil enforcement context. That work will serve him well at the US Attorney’s Office.”

This story has been updated.