President Obama has been seeking tempered metaphors to inspire hope about the economy while not putting his credibility at risk.

By DAVID E. SANGER

WASHINGTON - The formula for restoring national confidence - part good policy, part good politics, part good luck - can be hard to find. It eluded Herbert Hoover after the Crash of ‘29, Lyndon B. Johnson after the Tet offensive, Jimmy Carter after the energy shock and George W. Bush after Iraq turned from quick victory to bloody insurgency.

But President Obama has to try to do just that in a time of crisis. As the government announced recently that the nation’s largest banks had steered away from the precipice and that job losses were beginning to slow, Mr. Obama has carefully begun trying to mine any national leader’s most precious commodity in a crisis: optimism.

His past references to“glimmers of hope”were modestly upgraded at the White House on May 8, with his declaration - which he stumbled over, taking some of the assertiveness out of the line - that“the gears of our economic engine do appear to be slowly turning once again.”

His aides have been reaching tentatively for similar metaphors, then adding, as Mr. Obama quickly did, that real recovery is months, if not years, ahead.

Fear and aversion to risk have been part of the economy’s problems since the downturn began, and Mr. Obama’s aides have been highly attuned to the risks of a downward spiral of pessimism. In recent weeks, his economic team has begun flagging signs that the worst could be over, even as it carefully released the results of its bank examinations in a way that suggested a desire to reassure the financial markets and consumers. They got a bit of backing from the Federal Reserve chairman, Ben S. Bernanke, who forecast that the economy was likely to begin growing again by the end of the year.

“Remember this central paradox of financial crisis,”Lawrence H. Summers, Mr. Obama’s top economic adviser in the White House, said in mid-March, when every indicator was negative,“that while the problem was caused by excessive complacency and excessive optimism, what we need today is more optimism and more confidence.”

Mr. Obama’s own words on May 8 signaled that he was worried about the perils of getting out ahead of the numbers.

He spent more time talking about the letters he received from the desperate and out-of-work than he did dwelling on the decline in the pace at which Americans are losing their jobs. After all, 539,000 job losses in a single month is not exactly cause for celebration, even if it represents an improvement over the previous month.

“There’s a kind of artistry to this, isn’t there?”said Robert Dallek, the presidential historian best known for chronicling how Lyndon Johnson, the consummate politician, never led the public out of its view that everything was falling apart.“You don’t want to come out and say the recession is over. You want to do a version of Churchill’s line about how this isn’t the end, or the beginning of the end, but rather the end of the beginning.”

In Mr. Obama’s case, polls showed that a significant chunk of the public was predisposed to look for the bright side. The proportion of Americans who said the country was moving in the right direction rose to 41 percent in a New York Times/CBS News poll last month, from 15 percent in January just before his inauguration, even though by nearly every measure the economy was getting worse during that period.

But there are plenty of skeptics out there, from economic historians who know that history is littered with false recoveries, to those who argue that Mr. Obama has engineered a turnaround at the cost of phenomenal deficits and a huge new role for the government in the private sector.

Robert Reich, President Bill Clinton’s secretary of labor and one of Mr. Obama’s critics on the left, was on television recently arguing that to create this sense of optimism Mr. Obama’s team essentially skewed the results when it talked about the ability of the banks to survive a deeper downturn.

Timothy F. Geithner, the Treasury secretary, defended the administration’s approach.

“A huge part of the dynamic of a crisis is confidence,”he said in a telephone interview on May 8.

But administration officials said they recognized that the numbers that resound most with Americans were the unemployment statistics, and those were usually the last to recover.

They are also subject to surprise downturns, which explains Mr. Obama’s hesitance to describe the jobloss figures on May 8 as the beginning of an improving trend.

“The hardest part of this is balancing optimism with credibility,” said Mr. Dallek.“Hoover’s‘Happy days are here again’wasn’t credible. Bush’s‘Mission accomplished’became a running joke. No one wants to make that mistake again.”