Ben Bernanke, the chairman of the US central bank, the Federal Reserve, has played a central role in the global financial crisis...

...Mr Bernanke's four-year term as Fed chairman comes up for renewal in January, and his reappointment is now the subject of an increasingly bitter debate between right and left.

His role in the bail-out has come under fire from conservative Republicans and left wing Democrats, who believe that he betrayed his Republican roots by providing so much state support for the banks while ordinary citizens have suffered from the economic downturn.

Other economic conservatives fear that the huge Fed lending - along with a Federal government deficit that is expected to reach $1.7 trillion this year, is likely to prove highly inflationary, and are urging the Fed to unwind its big lending programme as soon as possible.

And some influential voices argue that, since the Fed performed poorly regulating the banks before the crisis, it should not be given the lead role now.

"Its credibility has been tarnished by the easy credit policies it pursued and the lax regulatory oversight..and the heavy influence that the banks have on the Fed's governance," say two former heads of the Securities and Exchange Commission, William Donaldson and Arthur Levitt...

...But Mr Bernanke has also attracted wide support among mainstream economists and investors for his handling of the crisis.

A petition from more than 250 prominent economists, including Yale's Robert Schiller and three Nobel Prize winners (Robert Merton, Eric Maskin, and Daniel McFadden) argues that the criticisms are putting the independence of the Fed at risk.

"When the Fed judges it's time to begin tightening monetary conditions, it must be allowed to do so without interference," they said.

And Mr Bernanke so far has one very important backer - President Barack Obama, the man who will decide later this year whether to reappoint him.

"He is doing a fine job in difficult circumstances," Mr Obama said at a press conference in June.

...The debate over Mr Bernanke's future, however, is also a debate about the future course of US economic policy after a year of unprecedented government intervention amid the deepest economic downturn since World War II.