I started to write an ironic, playful column comparing the Federal Reserve’s decline to that of the Yankees’ shortstop, Derek Jeter. Both are still pretty good compared to what else is out there, but they’re sure not what they used to be.

But the more I thought about the problems the Fed is having these days, the more I realized that what’s going on isn’t funny. It’s creepy.

A group composed largely of Republicans is running an advertising campaign against the Fed’s program of buying $600 billion of Treasury securities, and some Democrats are defending the program. Just before that ad campaign was announced, one of the Fed’s highest-profile governors, Kevin Warsh (of whom more later), who’d voted for the program, publicly questioned it—something I’ve never seen happen before.

All of this threatens to make the Fed look both uncertain and enmeshed in partisan politics, which would be devastating for its economic clout and moral authority. I’m no Fed worshipper, and am more than a little dubious about its “Quantitative Easing 2” program. But we need an independent central bank, not an organization that sticks its finger in the air to test the political winds before it moves.

Even before the Republican attack, our central bank was rapidly losing influence in the world, relative to other players. Part of that is because our country’s influence is shrinking—but another, big part of the problem is QE2, which is econ-speak for “printing money.”

The Fed board of governors was split publicly about whether to embark on QE2, making the Fed vulnerable right off the bat. The policy is being opposed publicly by other governments and central banks. That’s a problem, because we don’t want them dumping dollars. Financial markets—including the currency and commodities markets and parts of the long-term bond market—are sending a “no confidence” vote.

The first round of quantitative easing consisted of the Fed buying securities to forestall a financial panic last year by showing that it wouldn’t let major financial institutions run out of cash. That was imaginative and clever, and it worked.

No easy fix

But QE2 is a whole different game than QE1—and a riskier one. It’s a gamble on something that’s never been tried before. The idea is to goose the economy by reducing long-term rates by buying Treasury securities, supporting asset prices, and letting the dollar decline gradually in order to create  jobs here by making our exports cheaper and imports more expensive.

First, it’s not clear if the Fed can get those rates down—or whether it would help the economy much if it does.

Second, it won’t take much to turn the intended gradual decline in the dollar into a rout, given how financial markets tend to pile on when they smell a profit opportunity. “The trend is your friend,” as they say on trading desks.

This brings us to Kevin Warsh, a former Morgan Stanley mergers-and-acquisitions guy who’s been the Fed’s liaison with Wall Street since George W. Bush appointed him in 2006. In a striking speech last week, Warsh said that, “I am less optimistic than some that additional asset purchases [by the Fed] will have significant, durable benefits for the real economy.” He raised the prospect of QE2 being ended before the Fed meets its goal of buying $600 billion of securities.

Hello? What on earth is up with Warsh, who’s friendly with Bernanke? Beats me. Warsh declined comment. If I had to guess, my bet would be that Warsh’s speech wasn’t coordinated with the Republican attack, even though Warsh is a Republican (as is Bernanke).

But the Republican attacks, Warsh coming out against a policy he supported, and all that other opposition have put Bernanke in a tough position.

He was already making a high-stakes economic bet with QE2—and now it’s a political bet, as well. If QE2 succeeds, which might happen, it could help the economy. If it doesn’t work and Bernanke decides to pull the plug on it, it will look like he bowed to political pressure. If QE2 fails badly, it could imperil the dollar and our financial system—and protecting them is the Fed’s primary responsibility.

The Fed has been the world’s preeminent central bank for decades, and Derek Jeter has given the Yankees 15 great years. Jeter’s days as a star are numbered. I sure hope the Fed’s aren’t.

Also from Fortune.com:

How the banks can save Bernanke’s bacon