This letter from Senators McConnell, Boehner, Kyl, and Cantor crosses a line that shouldn't be crossed:
Dear Chairman Bernanke,
It is our understanding that the Board Members of the Federal Reserve will meet later this week to consider additional monetary stimulus proposals. We write to express our reservations about any such measures. Respectfully, we submit that the board should resist further extraordinary intervention in the U.S. economy, particularly without a clear articulation of the goals of such a policy, direction for success, ample data proving a case for economic action and quantifiable benefits to the American people.
It is not clear that the recent round of quantitative easing undertaken by the Federal Reserve has facilitated economic growth or reduced the unemployment rate. ...
We have serious concerns that further intervention by the Federal Reserve could exacerbate current problems or further harm the U.S. economy. ...
Sen. Mitch McConnell, Rep. John Boehner, Sen. Jon Kyl, Rep. Eric Cantor
I think speaking out individually is fine, e.g. a member of Congress stating his or her views on monetary policy in a speech is not a problem. That's part of the public dialogue.
But an official letter from members of the House and Senate to the Fed is more official, and more threatening to the Fed's independence than a speech from an individual member of Congress. Robert Reich explains the objections:
The Republican’s Latest Ploy to Keep the Economy Lousy through Election Day, by Robert Reich: ...To say it’s unusual for a political party to try to influence the Fed is an understatement.
When I was Secretary of Labor in the Clinton Administration, it was considered a serious breach of etiquette — not to say potentially economically disastrous — even to comment publicly about the Fed. Everyone understood how important it is to shield the nation’s central bank from politics.
If global investors suspect the Fed is responding to political pressure of any kind, investors will lose trust in the nation’s monetary policies. Even if the pressure is to tighten the money supply and keep interest rates high, it’s still politics. And once politics intrudes, lenders of all stripes worry that it will continue to intrude in all sorts of ways. The inevitable result: Lenders charge more for lending us money.
The letter puts Bernanke and his colleagues in a huge bind. If they decide against another round of so-called “quantitative easing” to lower long-term rates and boost the economy, they may look like they’re caving to congressional Republicans. If they decide to go ahead notwithstanding, they’re bucking the Republicans and siding with Democrats. Either way, they’re open to the charge they’re playing politics.
Congressional Republicans evidently don’t care. They want Obama out, whatever the cost. Besides, they’ve never met a government institution they don’t mind trashing.
There's more to it than higher interest rates. History tells us that politicizing monetary policy is a bad idea -- giving control of the money supply to politicians generally leads to high inflation -- and for this reason most countries have a monetary authority with some degree of independence. Thus, the GOP's politicization the Fed in the name of preventing inflation is puzzling (unless of course, inflation hawkery is cover for another agenda).