Last updated 11:06 a.m. ET

Stocks struggled to maintain gains Wednesday as surprisingly positive U.S. data barely offset concerns over the weak data out of China and Europe and jitters over the timing of a Spain bailout. The ADP private-sector employment report showed more jobs than expected were added in September. Meanwhile, the ISM service index also rose more than forecast in September. 

The Dow Jones Industrial Average ($INDU) was up 15 at 13,498. The S&P 500 ($INX) was up 3 points at 1,448. The Nasdaq Composite ($COMPX) was up 10 points at 3,130.

Also making headlines is Wednesday night's presidential debate, in which President Barack Obama and GOP challenger Mitt Romney will face off for the first of three sessions. No doubt, the economy and policies will be discussed.

Jobs data tops forecasts, but growth still slow
For now, attention turned to employment data. Private payrolls expanded by 162,000 in September, according to payrolls processing firm ADP. That was significantly above economists' expectations for 133,000, according to Briefing.com.

With employment data in the past two months showing much slower growth, investors had hoped the September data would show renewed growth. But the September figure, while above forecasts, is still a slowdown from the lower revised August increase of 189,000 jobs. ADP revised its July figure lower as well, pointing to a slower improvement than hoped. 

The ADP report is generally a good indicator of the Labor Department's jobs data, and it could foreshadow how Friday's nonfarm payrolls report will turn out. For Friday, economists expect a 120,000 increase in September nonfarm payrolls and that the unemployment rate will remain at 8.1%, according to Briefing.com.

Service sector grows at fastest pace since March

The Institute for Supply Management services index rose to 55.1 in September from 53.7 in August. Economists had expected the index to have ticked down to 53. Any reading over 50 indicates more companies are expanding instead of contracting.

On Monday, the ISM index on manufacturing surprised when it resumed growth as it moved into expansion territory, investors are hoping for another positive surprise.

Overseas data weak as Spain jitters weigh on stocks
On Tuesday, stocks first gained on hopes that Spain would soon ask for a bailout, but then they lost ground after Spain's prime minister dismissed the speculation that the country would seek a bailout as soon as this weekend.

European shares were lower Wednesday, weighed by Spain jitters and gloomy data. The final eurozone composite purchasing managers index for September fell to a four-month low, pointing to a steep monthly downturn for the region and an "inevitable" return to recession in the third quarter, according to survey compiler Markit.

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In Asia, too, data was weak. The Chinese nonmanufacturing purchasing managers index remained in expansion territory but fell to 53.7 in September from 56.3 in August, and consumer sentiment weakened for a third month in September to its lowest level since December.

The weak data, combined with uncertainty over the timing of a bailout for Spain, kept a lid on gains in Asia as many investors returned from a long weekend. Japanese and Taiwanese stocks ended lower, while Australian and Hong Kong stocks pared earlier gains. 

Stocks to watch
Best Buy (BBY) shares rose after Reuters, citing unnamed sources, reported that founder Richard Schulze and at least four private-equity firms have started examining the books of the world's largest consumer electronics chain in early steps toward what could become an $11 billion buyout.

MetroPCS Communications (PCS) closed up 18% on Tuesday after media reports said it confirmed that it's talking with Deutsche Telekom's T-Mobile unit about a possible merger. Deutsche Telekom would hold 74% and MetroPCS 26% in the combined entity, Financial Times Deutschland said on its website. Deutsche Telekom would also need to approve the plan. MetroPCS would receive $1.5 billion in cash, the report says.

Monsanto (MON) shares fell after the world's largest seed company reported a wider loss in the fourth quarter that was below analyst expectations. It also forecast 2013 earnings of no more than $4.32 a share, below the average analyst projection of $4.38 a share, according to data compiled by Bloomberg.

Apple's (AAPL) Asian component suppliers have reportedly begun mass production of a new tablet computer that is smaller than the current iPad, The Wall Street Journal reported, citing unnamed sources.