But Bernanke's prospects appeared to brighten Sunday, with three more senators, including Republican leader Mitch McConnell of Kentucky, predicting he'll be confirmed. A vote is expected later this week.
Still, the chance of Bernanke's defeat has unsettled Wall Street, contributing to last week's 4 percent loss by the Dow Jones industrial average, its worst performance in 10 months. If Bernanke were rejected, uncertainty over a successor would further roil global markets, at least in the short run.
Anxiety, along with sagging investments, could cause consumers and businesses to cut spending. Joblessness, already at 10 percent, could worsen. And the recovery might fail.
Economists who fear a double-dip recession - in which the recovery would collapse into another recession - regard it as a worst-case scenario. But they don't rule it out, either.
Lynn Reaser, chief economist for the National Association for Business Economics, is among them. She sees the likelihood of a double-dip as less than 50 percent.
"It will become more acute if there are delays in confirming a successor," she says, noting that the economic recovery remains fragile, with spending still weak, credit tight and job creation scarce.
"All the political angst over the confirmation couldn't have come at a worse time for the economy," Reaser says.
A Bernanke loss would heighten uncertainty about Fed policies on interest rates and stimulus measures. In part, that's because Bernanke devised the unconventional supports for the economy and likely knows how best to safely wind them down, notes Edward Yardeni, chief investment strategist at Yardeni Research.
But even more worrisome for the markets and the economy would be if Bernanke's Senate foes are seen as having meddled with the Fed's independence for political reasons.
The dollar would likely fall. Higher interest rates and inflation fears would follow, stoked by uncertainty and shaken confidence. And all that would probably unsettle consumers and business, making them less likely to spend, hire or invest.
Bernanke's confirmation, which had seemed assured, was suddenly thrown into doubt last week as resistance grew among some Senate Democrats. And some senators who had supported Bernanke said they were now undecided.
The Fed chief's term expires Jan. 31. If Bernanke isn't confirmed by then, Vice Chairman Donald Kohn is expected to step in as chairman and run the central bank temporarily.
Bernanke is widely credited with helping to prevent the recession from turning into a second Great Depression. But his support of Wall Street bailouts during the height of the financial crisis has angered Americans struggling with 10 percent unemployment and soaring home foreclosures.
Backlash from Democrats over Bernanke's role in the bailouts intensified after Democrats suffered a stunning upset in the Massachusetts Senate race. Democrats are eager to appear allied with ordinary Americans disgusted with Wall Street's excesses.
Higher interest rates that could follow a Bernanke defeat would make it costlier for the government to pay down its record-high debt. Right now, low rates are allowing the Treasury Department to manage its debts.
If investors think the White House and Congress will choose a successor who would keep the Fed pumping money into the economy and hold interest rates at record lows for too long, it would erode trust in the Fed's oversight of the economy.
Continued low rates would please many ordinary Americans. But it would risk creating new speculative bubbles and stoking inflation.
Some economists say that in long run, they most fear that global investors would see a rejection of Bernanke as setting a precedent for Congress to intrude on"monetary policy." That refers to the Fed's decisions on whether and when to adjust rates to influence economic activity, inflation and employment.
The Fed's independence in monetary policy is vital to public confidence in the central bank. If it's undermined, the Fed could lose its credibility on Wall Street, which would fan inflation pressures and send up interest rates, choking the economic rebound.
"Do we get to the point where instead of having an independent Fed chairman who keeps his hand on the wheel and does what is right for the economy, we have a Fed chairman spinning the wheel at the behest of Congress?" says Peter Morici, an economist at the University of Maryland.
Speaking on Sunday talk shows, Senate Republican leader McConnell and Sen. Dick Durbin of Illinois, the No. 2 Senate Democrat, predicted the Senate would approve Bernanke's confirmation. And over the weekend, President Barack Obama phoned Senate allies and was given assurances that Bernanke's approval is likely.
The Fed chief's supporters need 60 votes to stop opponents from blocking confirmation, though the confirmation vote itself requires only 50 votes. Sen. Bernie Sanders, an independent liberal from Vermont, and Republican senators Jim Bunning of Kentucky, Jim DeMint of South Carolina and David Vitter of Louisiana are leading an effort to block confirmation. All told, about a dozen senators have indicated they'll vote against Bernanke.
White House spokesman Robert Gibbs told "Fox News Sunday" that lawmakers would send a worrisome message to financial markets by "playing politics in any way" with Bernanke's nomination.
Investors have generally signaled their faith that Bernanke has the know-how and political will to sop up the money the Fed pumped into the economy during the financial crisis and prevent an outbreak of inflation.
A major challenge for the Fed will be deciding when to start boosting rates and when to phase out some big emergency economic revival programs.
One such program is the Fed's purchase of mortgage securities from Fannie Mae and Freddie Mac, as a way to keep mortgage rates down. The Fed is on track to buy $1.25 trillion in those securities by the time the program is scheduled to end at the end of March. But the Fed hasn't ruled out continuing to buy mortgage securities after then to support the economy.
First appointed to the Fed by Republican President George W. Bush, Bernanke is likely less objectionable to Republicans than other potential alternatives, such as White House economic advisers Larry Summers or Christina Romer, or Janet Yellen, president of the Federal Reserve Bank of San Francisco.
A change in leadership wouldn't immediately mean a shift in Fed policy. That's because rates are expected to remain a record lows through much of this year to nurture the recovery.
No Fed chairman has been rejected by the Senate. The most "no" votes cast against a Fed chairman was Paul Volcker in 1983. The count: 84-16.