Politicians have put a lot of pressure on the Fed to do one thing or another this year. GOP presidential nominee Mitt Romney expressed an opinion widely held in his party when said that he didn't think the Fed should start a fresh round of bond-buying, known as quantitative easing or QE3.

"I don't think a massive new QE3 will help the economy," Romney told CNN's Gloria Borger last month. Bernanke is in some ways an unlikely target for conservatives--he is a Republican first appointed to the Fed by President George W. Bush.

This Tuesday, Sen. Bob Corker, R-Tenn., who sits on the Banking Committee, issued a statement urging Bernanke not to launch a third round of bond-buying. "I hope Chairman Bernanke will show humility and make clear there are limits to what monetary policy can achieve," Corker said, adding that QE3 would "only be exacerbating the [economic] problem."

Democrats, too, have urged the Fed toward a particular course, having called on the central bank to do more to help the ailing economy for months. "I would urge you to take whatever actions you think would be most helpful in supporting a stronger economic recovery," Sen. Chuck Schumer, D-N.Y., said to Bernanke in a July hearing.

Economists and analysts have wondered for months how much the Fed is able to shut out the din, particularly as the bank faces threats to the institutional independence that Bernanke so highly values. "The political backlash [among the Fed's Republican critics] that could ensue from a new large round of bond buying may be a restraining factor in the [Fed's] decision," analysts at political risk research and consulting firm Eurasia Group said in a research note in advance of Thursday's announcement.

"The bottom line is that an aggressive Fed move would be walking into political crossfire at exactly the moment when voters are most open to forming new opinions on policy issues," the consulting firm wrote. If Republicans paint the Fed's actions as compensation for President Obama's failed policies--which the Romney campaign has already sought to do--then Bernanke could lose longer-term public support, the Eurasia Group cautioned.

Stepping into the political spotlight through aggressive--and divisive--policy action also carries the risk that the institutional threats the Fed faces will gain wider support. Legislation that would allow Congress to audit the bank's monetary-policy decisions--which Bernanke warned would have a "chilling effect" on the bank's decision-making process--passed the House this summer, 327-98.

Sen. David Vitter, R-La., who supports the Senate version of the Fed-audit legislation, condemned the Fed's actions on Thursday. "Chairman Bernanke and the Federal Open Market Committee are clearly feeling tremendous pressure to bail out the economy because of President Obama's struggle to turn around the jobless numbers," he said in a statement.