Just because President Obama and Congress haven't cut a deal to avoid tax hikes and spending cuts that will threaten a new recession, is that any reason for investors to freak out and sell stocks, bonds, and retirement funds?

Investment advisers - including some notable ones in the Philadelphia region - trying to preserve healthy 2012 gains in the markets after a decade of pathetic results, are pushing clients to stay calm about the mess in Washington.

While the financial markets will be nervous until there is a deal, "the underlying economic data continues to offer encouraging signs," wrote a hopeful Mark Luschini, chief investment strategist at Philadelphia-based brokerage Janney Montgomery Scott, in a note to clients Wednesday.

Though "investors are being bombarded with suggestions to sell, Vanguard urges you to be cautious," says investment analyst Sarah Hammer in one of a string of hand-holding video and written commentaries the Malvern-based fund giant has posted to try to persuade clients to hold onto their retirement accounts instead of dumping them to buy, say, gold or high-yield, high-risk junk debt.

Obama was scheduled to return to Washington Wednesday night from a Christmas vacation in Hawaii. Congress is to reconvene Thursday. If the president and the Senate and House fail to reach agreement, a combined $500 billion of tax increases and federal spending cuts could jolt the U.S. economy.

The overhang of the fiscal cliff deadline did not overwhelm the markets Wednesday. The Dow slipped 24.57, down just 0.19 percent.

There is a chance for an abridged deal before Tuesday that would allow some taxes to increase for wealthier Americans and fewer budget cuts. Or, an agreement might be achieved in the first weeks or months of 2013.

But many observers think either of those developments would still unnerve financial markets and adversely affect the economy at a time when housing and other indicators give some confidence that the new year could see fast improvement.

Some of the consequences of tumbling over the cliff would be immediate, such as an end to unemployment benefits. Others, such as huge cuts in government spending, would have a cumulative effect that would spread over 2013, analysts said.

The fiscal cliff has the attention of most Americans. So what's the worst that can happen?

Asset prices are supposed to reflect the cash they will generate for their owners. But a feared or actual drop in government spending that companies depend on, plus increases in federal tax breaks that consumers and businesses count on, "may disrupt those cash flows for a couple of quarters," said James Meyer, chief investment officer at $1-billion-asset Tower Bridge Advisors in Conshohocken.

Such a situation could temporarily depress securities values, but they will recover, "assuming Washington doesn't go so far as to allow the U.S. to default on its debt and really create a mess," Meyer added.

"The odds of that are small," he said, but not zero. The possibility that lawmakers could again threaten to stiff the Fed and other government creditors instead of making a deal could push investors to sell.

A government default would likely trim stock values, especially for "tech, industrials, basic materials, money-center [large investment] banks, and high-profile retailers," Meyer explained, as well as other "stock-market sectors that tend to swing higher in a rising market and lower when prices fall."

The White House and some Republicans in Congress claimed to be close to a deal 10 days ago, but neither side feels a lot of incentive to give up on the last few hundred billion dollars of tax hikes or spending cuts, Meyer told clients of West Conshohocken-based brokerage Boenning & Scattergood in a report Wednesday.

Obama "thinks he earned a mandate in the election to do things his way," Meyer said, instead of compromising as much as he did in a similar situation last summer. But neither he nor his rivals are strong enough to force a "one-sided agreement," Meyer said.

Investors still doubt Congress will force a default. Stocks rose an average 1 percent a month during 2012. They remain priced, Meyer observed, as if traders believe the "skies will begin to clear by March and life will get back to normal."

But what does normal mean in today's Washington?

"Few expect the new Congress to be any more productive than the last one," Meyer said, because it again will be the product of a largely divided electorate.

"There will be lots of debate about gun control, tax reform, immigration, and energy. But the odds of getting anything done beyond what is essential, like raising the debt ceiling, is problematic at best."