The unemployment rate in November was 7.7 percent — it has not been below 6.5 percent since September 2008 — while the rate of inflation in recent months is lower than the 2 percent annual rate that the Fed considers healthiest.

“Imagine that inflation was running at 5 percent against our inflation objective of 2 percent,” Mr. Evans said in a September 2011 speech first describing the proposal. “Is there a doubt that any central banker worth their salt would be reacting strongly to fight this high inflation rate? No, there isn’t any doubt. They would be acting as if their hair was on fire. We should be similarly energized about improving conditions in the labor market.”

That argument was easier to win because inflation is under control, and the Fed expects the pace of price increases to remain at or below 2 percent through 2015. But in perhaps the clearest indication of the Fed’s philosophical shift, the Federal Open Market Committee said Wednesday that it would not relent in its focus on unemployment unless the medium-term outlook for inflation rose above 2.5 percent.

The change was supported by 11 of the committee’s 12 members. The only dissent came from Jeffrey M. Lacker, president of the Federal Reserve Bank of Richmond, who has repeatedly called for the Fed to do less. He says he believes the policies are ineffective and could inhibit the central bank’s ability to control inflation.

The Fed has held short-term interest rates near zero since December 2008, and it said in September that it intended to do so until at least mid-2015. The forecast was intended to reduce borrowing costs by persuading investors that interest rates would remain low for longer than they might have expected.

Mr. Bernanke said Wednesday that the shift to economic targets was not significant in the short term because the Fed still expected its goals to be reached no sooner than mid-2015. He said the bank chose 6.5 percent as its target because analyses showed that full-throttle stimulus beyond that level of unemployment could result in higher inflation.

Stock prices jumped after the Fed released its policy statement at midday, then began falling during Mr. Bernanke’s news conference about two hours later as he insisted that the Fed was not significantly increasing its efforts to bolster the economy. The Standard & Poor’s 500-stock index rose 0.04 percent on the day.