Stocks ended mixed Tuesday despite oil prices holding near $50 a barrel, with the Dow suddenly giving up its early gains, as chatter on the Internet speculated that early exit polls had Sen. John Kerry leading the presidential election in key swing states.

The mid-afternoon turnabout wiped out gains built on declining oil prices and investors' hopes for a conclusive presidential election.

The Dow Jones industrial average (search) slipped 18.66 points, or 0.19 percent, to close at 10,035.73, based on the latest data. The Standard & Poor's 500 Index (search) eked out a gain of just 0.05 of a point, or unchanged from a percentage standpoint, to close at 1,130.56, its sixth day of gains. And the technology-laced Nasdaq Composite Index (search) added 4.92 points, or 0.25 percent, at 1,984.79.

Earlier, the Dow traded as high as 10,132.99, and the Nasdaq composite broke through the 2,000 mark for the first time in about four months. The Dow lost about 60 points in 18 minutes.

"What we are hearing is that there is some feedback coming back from Ohio, that there could be a closer outcome out there or John Kerry could even potentially win that state," said Evan Olsen, head of equity trading at Stephens Inc.

Voter turnout was unusually high as Americans voted to decide whether President Bush or Sen. John Kerry would be the next U.S. president.

Some investors said a Kerry sell-off might be short-lived.

"Fundamentally, there is nothing to indicate that Kerry will be bad for the market," said Som Dasgupta, head of equities trading at PNC Corporate Bank. "There are all kinds of statistics around (that) if the incumbent is a Republican and a Democrat wins, then the initial market sell-off is 1.5 percent. Then the market comes back up around 2.8 percent through January."

Investors welcomed another drop in oil prices that took crude futures below $50. A barrel of light crude for December delivery closed at $49.62, down 51 cents, on the New York Mercantile Exchange (search) — the lowest settlement price since Oct. 4.

Most analysts agreed that a clear winner by Wednesday morning — or at least a credible claim of victory by either candidate — would boost the market. But if the election appeared to be headed for a prolonged court battle like in 2000, stocks could fall sharply.

"The worst thing that could happen is a contested election, because you'll see this bull run we've had over the past five or six days dissipate," said Peter Cardillo, chief strategist and senior vice president at S.W. Bach & Co. "If somebody can declare victory, then this bull run could extend right through to the end of the year."

Trading volume was higher than expected throughout the session, as early confidence in a quick victory was wiped out by signs that it would indeed be a close contest. In 2000, the markets endured their worst post-election November since Harry Truman's upset victory in 1948.

"I think there's some money just waiting to come in once we have a winner in the election," said Michael Sheldon, chief market strategist at Spencer Clarke LLC. "The uncertainty of 2000 is certainly hanging over the market, and we're hoping we don't get a repeat. If we don't, then we have a strong positive bias and a very healthy technical market."

A Kerry victory could affect defense and health care stocks, said John O'Donoghue, managing director of listed trading at CSFB.

General Dynamics Corp. (GD) fell $2.19, or 2 percent, to $100.15. The company was seen as a Bush stock since it makes hardware like military vehicles and ships. It was the biggest percentage decliner in the S&P defense index.

Energy-sensitive issues, including airlines, attracted buyers. Continental Airlines (CAL) shares rose 44 cents, or 4.6 percent, at $10, and Northwest Airlines Corp. (NWAC) added 3.6 percent, or 33 cents, to $9.53.

The American Stock Exchange airline index (search) rose 3 percent, hitting its highest point since mid-July.

Emerson Electric Co. (EMR) gained $1.25 to $65.53 as the diversified manufacturer saw its net income jump 28 percent. The company beat Wall Street profit forecasts by 5 cents per share.

National Semiconductor Corp. (NSM) lowered its profit forecasts for the current quarter, citing sluggish sales and high inventories, much as Intel Corp. (INTC) had done in September with its mid-quarter report. National Semi tumbled 29 cents to $16.40, while Intel climbed 17 cents to $22.61.

Consumer products maker Clorox Co. (CLX) fell $1.38 to $53.77 after reporting that its first-quarter earnings fell 5 percent due to one-time charges stemming from a restructuring effort. The company still beat analysts' expectations by 3 cents per share.

Insurance stocks were mixed as Merrill Lynch downgraded Aon Corp. (AOC) and Willis Group Holdings Ltd. (WSH) in response to New York Attorney General Eliot Spitzer's investigations of the two companies. Aon lost 19 cents to $20.46 while Willis added 4 cents to $36.

Media reports said Time Warner Inc.'s (TWX) struggling America Online unit would lay off 700 workers as the online service worked to stem a tide of subscriber defections. Time Warner was down 10 cents at $16.28 on the news.

The Russell 2000 index of smaller companies was down 1.58, or 0.3 percent, at 585.42.

Overseas, Japan's Nikkei stock average rose 1.43 percent. In Europe, Britain's FTSE 100 closed up 0.42 percent, France's CAC-40 climbed 0.85 percent for the session, and Germany's DAX index gained 0.62 percent.

Reuters and the Associated Press contributed to this report.