The Nasdaq rose 0.2%, but the NYSE composite fell 0.7%. The Dow and the S&P 500 slid 0.4% and 0.3%, respectively. The Philadelphia semiconductor index leapt 3.1%, boosting the Nasdaq.

Volume was modestly higher on both major exchanges. The higher volume, combined with the price slippage, added a distribution day to the Dow, NYSE composite and S&P 500.

A distribution day involves a loss on a major index in rising volume. It points to institutional selling. Five or six in several weeks can kill a market uptrend.

The current load is getting a bit heavy for the NYSE composite and the Dow, but the Nasdaq's load is light. The major indexes trimmed losses and, except for the NYSE, closed near session highs.

Financial commentators rounded up the usual suspects in explaining Wednesday's selling.

Some market watchers blamed a strengthening U.S. dollar, which is bad news for commodity-tied and other types of stocks. Others noted that durable goods orders in September were disappointing. Still others pointed to nervousness surrounding the Federal Reserve's expected plan to buy Treasury bonds.

But there might be another factor at play. In each of the past five midterm election years, the market has suffered one or more distribution days in the week before Election Day.

Jitters before an election aren't surprising. It's natural to take money off the table to protect against a surprise, especially if there have been sharp gains. Since its late-August low, the Nasdaq has risen 19% .

But money wasn't coming off the tech table Thursday. Network stocks were strong, with F5 Networks (FFIV) popping 15% on strong results reported late Tuesday, and Akamai Technologies (AKAM) and Aruba Networks (ARUN) notching 4% and 8% gains, respectively.

Still, roughly 10 of every 13 industry groups fell. Retail led the losers, with restaurants taking the hardest hit. Of the 14 restaurant stocks, several stumbled in fast trade. Panera Bread (PNRA) chopped off 5%. Buffalo Wild Wings (BWLD) clipped 12% intraday but finished only 3.5% lower. Also, BJ's Restaurants (BJRI) corrected 6%, after rumbling 22% higher over the previous three sessions.

Chipotle Mexican Grill (CMG), the top restaurant stock, held up rather well. It edged down 0.3% in above-average trade.

After the close, Las Vegas Sands (LVS) jumped 10% after trouncing estimates. But Cavium Networks (CAVM), which broke out of a base in the regular session, dropped 2% despite beating estimates.