The stock market is starting to crack under pressure of the week-old federal government shutdown that potentially could snowball into a default on U.S. Treasury obligations late next week.

"Within the last 48 hours our phones started to light up, and we're hearing from the normal suspects — the clients who get nervous first," said Ben Marks, chief investment officer at Marks Group Wealth Management of Minnetonka in an interview Tuesday.

"We say, 'Put things in perspective.' There have been 17 government shutdowns since 1977. Most last a few days. The last one in 1995 lasted 20-some days. It's not like this has never happened. The market usually goes down a few percent."

During the bruising 2011 budget battle on Capitol Hill, the Standard & Poor's 500 index sank more than 15 percent in value. That was followed by a two-year run to record highs last month.

Since the Obamacare-inspired federal shutdown on Oct. 1, the S&P 500 index has declined 2.2 percent and the Bloomberg-Star Tribune 100 index of Minnesota's biggest public firms has declined 5 percent through Tuesday's trading.

That followed year-to-date gains in the S&P 500 of 17.9 percent and 32.5 percent in the Star Tribune 100 index through September.

Analysts say the Star Tribune index, which consists largely of smaller-value companies that trade in lower volume, tends to gyrate more than larger, more liquid stocks where cautious equity investors are likelier to hide — before they exit the market in fear.

"The best answer may be to do nothing," said Biff Robillard of Bannerstone Capital Management. "There's not much to be gained from overthinking this. In 2011, I believe there was a 19 percent decline from peak to trough, but by Oct. 5 it was over. I was pretty nervous in August and September [of 2011]. It sounds like pabulum, but it's fairly good advice to sit tight at times like this. I've just been watching for 35 years and I really don't know how to exploit fiscal policy fights on deadline."

Said Marks: "As this drags on, investor anxiety increases. You have to look strategically. There are opportunities. We have been buying some … health care stocks. We have put some client money to work [for those] who wanted to get more invested with long-term money. I think this goes to the final hour or beyond. There will be some compromise and concessions."

Jim Paulsen, chief investment strategist at Wells Capital Management, has been a vindicated market optimist since the bleak days of early 2009.

He told investors that short-term Washington budget fights overshadow solid economic developments, including a growing economy.

"These include restoring financial health to the U.S. government, developing a long-term plan for addressing the economic impact of aging developed world demographics, promoting a course for U.S. energy independence, and finally, reformatting the U.S. health care insurance system," Paulsen said. "We offer these illustrations to suggest most worry too much about the drama, which is our government.

"Relax a little. … For while Washington argues and begins the new fall season with yet another fiscal cliffhanger, Adam Smith is busy solving many of the big economic problems of our day."