Now that Lawrence Summers has taken himself out of the running to become the next chairman of the Federal Reserve, President Barack Obama should look for a truly “post-crisis” candidate who can reassert the Fed’s independence and move away from the unusual policies of the last six years.

During the credit crunch of 2007-2008 and its aftermath, it was proper and right that the Fed and the Treasury Department were joined at the hip: Both had an interest in easing the financial crisis, which took precedence over everything else. It was also proper for the Fed to aggressively lower interest rates.

But the next chairman will have to decide when to trim the Fed’s portfolio, swollen with its extraordinary program of bond purchases. And it will have to raise short-term interest rates, which are currently near zero. It may be sooner, it may be later — the moment will come. Money cannot be free forever.

To make this decision, the Fed should be led by a fresh pair of eyes — one not compromised by its current policies. That would rule out Janet Yellen, the Fed vice chairman and odds-on favorite. It would also exclude her predecessor, Donald Kohn, as well as former Treasury Secretary Timothy Geithner (not to mention Summers, who was director of the National Economic Council).

Since 2007, Fed policy has been gauged through the prism of the financial crisis. Its almost exclusive mission has been to avert a depression. Since then, unemployment has fallen to 7.3 percent from 10 percent. That is still too high, yet close enough to the “new normal” for other priorities to get attention. For instance, ultra-low interest rates are punishing savers and discouraging thrift, not a healthy condition. As we’ll recall from the mortgage crisis, chasing yield can lead to big trouble. The still-slow economy also remains a risk; this is why the next Fed chairman will have to strike a careful balance.

History suggests that moving away from zero rates will be unpopular and difficult — especially for a Fed on cozy terms with the White House. In the early 1970s, President Richard Nixon told economist Arthur Burns, his new Fed chief and a political ally: “You see to it. No recession. Burns complied by priming the pump, and runaway inflation resulted.

Alan Greenspan, who ran the Fed before Ben Bernanke, had better results on inflation, but he also was compromised by his palpable eagerness to be a popular administration insider.

If the next chairman isn’t a Washington hand, who should it be? It is too soon after 2008 to tap an executive from Wall Street, which bundled the toxic mortgages at the heart of the crisis. That rules out William Dudley, president of the New York Fed and a former Goldman Sachs Group Inc. economist.

It’s worth recalling that the central bank is a bank or, rather, a government board with an affiliated network of privately owned reserve banks. Just as individuals go to a bank to park their savings and to seek loans, banks need an institution to house their reserves and to provide them with credit. That is why the Fed was created: to be a banker to the nation’s banks, a backstop to other lenders.

This leads to a heretical thought: What about a banker to run the central bank? Not a banker who bundled mortgage securities, but a traditional banker who would remind the nation that issuing loans can be a noble calling.

In recent times, the Fed has been dominated by policymakers. Bernanke was an academic and then a government official (Yellen has a similar background, though she also ran the San Francisco Fed). Greenspan was a consultant and adviser to President Gerald Ford. Geithner was a Treasury official before taking over the New York Fed.

But Paul Volcker, the most independent Fed chairman in history, was a banker — president of the New York Fed and an economist at Chase Manhattan Bank when Chase was a lender to corporations. William McChesney Martin, who served from 1951 to 1970, was a traditional banker as well as a regulator. Although he knuckled under to pressure from President Lyndon Johnson toward the end of his tenure, Martin set the standard for Fed independence, proclaiming it was his job to “take away the punch bowl” when the party warms up.

The punch brewed by Bernanke consists of trillions of dollars in banking reserves that private banks now hold as credits. As these reserves are converted into loans, the economy will heat up and the Fed’s new chief will need to dampen the merrymaking.

Rather than look for a consultant, academic or regulator, Obama should nominate a chairman with an institutional grasp of the banking system. The next Fed chief should be a banker.

Roger Lowenstein, a former Wall Street Journal reporter and columnist, is writing a book on the origins of the Federal Reserve System.