"People might look at that uncertainty and say, 'I'm happy with that, and now I'll take some money aside, and sell,'" he says.
Q: What about after Jan. 1?
Deal or no deal, many investors don't expect the effects of the "fiscal cliff" to linger in the stock market for too long. One big reason is that everyone has seen it coming for months.
"We're not overly concerned," says David Hefty, CEO of Hefty Wealth Partners in Auburn, Ind. "The thing to keep in mind is that what hurts investors, what hurts the market, are things that are unexpected."
He adds: "Everybody has 2008 burned into their minds. They think the fiscal cliff will be the next 2008 event. A 2008 event is when nobody sees it coming, and everyone is blindsided. Nobody's going to be blindsided by this."
Hefty says he'll watch whether the Federal Reserve continues its policy of pumping money into the economy, and fundamentals like housing and unemployment, to decide how to invest in 2013.
"We're looking at two key things that matter the most," he says. "The 'fiscal cliff' isn't one of them."
Donald Quigley, the co-manager of the Artio Total Return Bond mutual fund, is more wary of the "cliff" for its political impact than its economic impact. If Republicans and Democrats can't reach a compromise, he says, the world could take that as a sign that the U.S. government is dysfunctional.
"It basically says, 'We really don't have our act together,'" Quigley says. "To have to admit that your country is ungovernable is not the best way to run a country."
Q: What if there's no deal?
The impact of higher taxes and lower government spending would be felt only gradually, and Congress could always repeal them later, which is why many analysts don't expect panic.