Your Money, Your Retirement, and the 2016 Presidential Election - What changes will you need to make to your portfolio should Hillary Clinton become president? What happens to your investments should Donald Trump become president? Join us on Sept. 12 as our panel of the world's top financial experts provide trusted information on the investment risks and opportunities that arise with the upcoming presidential election in November. [Learn more about the event and RSVP.]

Stocks were mixed mid-afternoon Thursday as Wall Street awaited a critical U.S. jobs report on Friday. 

The S&P 500 was down 0.17%, the Dow Jones Industrial Average fell 0.11%, and the Nasdaq rose 0.14%.

The official jobs report for August, the most closely watched release of the month, will be under even more scrutiny ahead of the September Federal Reserve meeting. Economists expect the pace of jobs growth in August to slow after blockbuster readings in June and July. Analysts at TD Securities expect 189,000 jobs to have been added to the U.S. economy, while the unemployment rate will dip to 4.8%. The U.S. economy added 255,000 jobs in July.

"Investors are going to have to seriously consider the possibility of a September hike if we get a strong set of numbers on Friday," said Luke Bartholomew, investment manager at Aberdeen Asset Management. "Everyone had largely discounted this scenario until now, so we might get a wobble in risk markets if the numbers are good. It could be one of those perverse situations where good economic news is bad for financial markets."

The ISM Manufacturing Index for August fell into contractionary territory at 49.4 from 52.6 in July, well below an expected reading of 52.2. A strong U.S. dollar and weak global demand have impeded manufacturing growth for months.

A separate reading on manufacturing showed a slight drop in August. The August U.S. PMI Manufacturing Index eased to 52 from 52.9, though output growth remained at its July high, its best level in eight months.

"This raises the bar in terms of how strong the payroll gain in August (reported tomorrow) needs to be to push the Fed to act in September," RBS analysts wrote in a note. "Without signs of further progress on inflation and with these data raising some warning flags over a loss of momentum (at least in manufacturing) post-Brexit, we continue to believe this cautious, risk-adverse Fed is more likely to wait for more information rather than hike in September."

Crude oil ended the day sharply lower as worries over a supply glut continued to mount. Oil slumped on Wednesday after a larger-than-expected increase in weekly domestic inventories. International oil producers continue to pump output at record levels. 

West Texas Intermediate crude ended Thursday's session 3.5% lower at $43.16 a barrel, its lowest close since Aug. 10. 

Costco (COST) - Get Report fell 3% after reporting a flat reading on comparable-store sales for August and the recent quarter. Excluding gas and currency exchange, sales rose 2% for August and 3% over the quarter. Analysts had expected same-store sales to increase 1.3% in August and 3.4% adjusted to exclude gas.

Costco is a holding in Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells COST? Learn more now.

Walmart (WMT) - Get Report shares were up 2% following reports of job cuts. The world's largest retailer will reportedly cut 7,000 back-office positions, according to The Wall Street Journal.

Ford (F) - Get Report shares fell 1.5% after the automaker reported an 8.4% decline in sales over August. Passenger car sales slumped 25% to 52,148 last month, while truck sales declined 1.6%. Fiat Chrysler (FCAU) - Get Report reported a far better August with total unit sales up 3% and passenger car sales down 13%. Sales at General Motors (GM) - Get Report in August fell 5.2%. The stock fell 0.4%.

Campbell Soup (CPB) - Get Reportslipped 6% following a disappointing fourth quarter. The packaged food company swung to a loss of 26 cents a share from earnings of 5 cents a share a year earlier. Adjusted earnings of 46 cents a share missed consensus by 50 cents. Campbell's revenue of $1.687 billion came in short of consensus of $1.694 billion.

Joy Global (JOY) fluctuated after reporting a quarter in which weak demand for mining equipment hurt results. Total bookings fell 17%, dragged on by a 46% slump in original equipment orders. Japanese company Komatsu announced in July that it would purchase Joy Global for $2.9 billion.

Box (BOX) - Get Report was 1% higher after reporting a narrower quarterly loss than expected and a double-digit jump in revenue. The file-sharing developer reported a loss of 14 cents a share over its second quarter, a nickel narrower than forecast. Revenue jumped just over 30% to $95.7 million. (CRM) - Get Report fell 5% after issuing light guidance for its current quarter. The cloud software developer expects current-quarter earnings of 20 cents to 21 cents a share on revenue no higher than $2.12 billion. Consensus was for earnings of 24 cents a share and sales of $2.124 billion.

Infoblox (BLOX) was 3% higher after narrowly beating profit and sales estimates over its recent quarter. The cybersecurity firm earned 8 cents a share, 2 cents above estimates, while revenue of $86.3 million bested estimates by $1.8 million. Infoblox jumped over Wednesday's session on reports it has begun the process of selling itself after pressure from activist investor Starboard Value.

Ciena (CIEN) - Get Report climbed after posting better-than-expected earnings for the third quarter. The telecom-equipment maker reported adjusted earnings of 42 cents per share, topping analysts' estimates of 38 cents per share. Revenue rose 11.2% year-over-year to $670.6 million but missed analysts' projections of $672.2 million.

Cynapsus Therapeutics CYNA spiked after the Toronto-based pharmaceutical company announced it would be purchased by privately-owned Marlboro, MA-based drugmaker Sunovion Pharmaceuticals for about $624 million. The deal values Cynapsus at $40.50 a share. 

Wynn Resorts (WYNN) - Get Report rose after Macau gaming returned to growth for the first time since May 2014. In August, gross gaming revenue at Macau rose 1.1% to $2.4 billion, which topped analysts' expectations for a decline of 1.5%.

Stocks ended August on a dour note Wednesday as another selloff in crude oil pressured the energy sector and speculation over interest rates continued to cause jitters. The S&P 500 ended August with a slight monthly loss.

The number of new claims for unemployment benefits in the U.S. increased by 2,000 to 263,000 in the past week. Analysts had expected an increase to 265,000.

Productivity over the second quarter fell 0.6%, according to the Bureau of Labor Statistics, which came in as analysts had expected. Output increased 1.1%, while hours worked rose 1.7%.