The broad-based S&P 500 (^GSPC -0.28%) finally had a day of positive economic data that it could rely on to push higher, but it wound up being thwarted by negative geopolitical issues that pressured markets from the opening bell.

Perhaps no story is of bigger concern than the escalating tensions between Russia and Ukraine, especially with Russia invading Ukraine's Crimean peninsula after assuring the rest of the world that it would not do so just days before. The potential for a conflict here is rising, and the prospect that it could negatively affect global growth is quite real.

On the other side of the coin, U.S. personal spending for January came in much higher than expected, with growth of 0.4% compared with expectations of just 0.1% growth. Personal spending is an important indicator, since consumer spending accounts for the lion's share of GDP growth.

Conversely, construction spending was weaker in January, growing by just 0.1% compared to 1.5% in December. This isn't too much of a surprise given that the weather in January practically shut down the East Coast on a number of occasions and thwarted a number of residential and enterprise construction projects.

By day's end, investors made it very clear that they're concerned with the crisis in the Ukraine and pushed the S&P 500 decisively lower by 13.72 points (-0.74%) to close at 1,845.73.

Leading the charge to the upside today is fuel cell systems developer Plug Power (PLUG 20.10%), which rose 24.6% after an analyst at Cowen & Co. bumped Plug's price target higher by 10% to $5.50. The price target upgrade comes on the heels of a big contract award, which we discovered last week came from Wal-Mart (WMT 0.32%) to provide fuel-cell systems for forklifts in select warehouses across the United States. Cowen also notes that this could open the door to more contracts in the U.S. and in possibly in Europe. The Wal-Mart contract is a big step forward for Plug Power in validating the viability of its fuel-cell technology, but it remains to be seen if the company can continuously deliver contract growth, or if this was an anomaly.

Shares of small-cap biopharmaceutical Dendreon (NASDAQ: DNDN) also rose strongly today, by 14.9%, after it reported better-than-expected fourth-quarter results before the opening bell. For the quarter, Dendreon delivered an 8% decline in Provenge revenue, its metastatic prostate cancer immunotherapy vaccine, to $74.8 million while its loss shrank by 44% to just $0.17 per share. By comparison, Wall Street had been expecting Dendreon to report a wider loss of $0.24 per share on $72.9 million in revenue. Investors seem pleased that Dendreon is making serious strides toward curbing its cash burn, but I'd caution that its goal of becoming cash-flow breakeven is still very much up in the air. Dendreon is going to need a strong launch in Europe if it has any hope of stemming its losses in 2014. I would suggest investors keep to the sidelines until such time as when Dendreon becomes cash flow breakeven.

Finally, ethanol producer Pacific Ethanol (ALTO 2.10%) continued its strong gains after reporting market-topping fourth-quarter results last week and tacked on 9.9% by day's end. Last week Pacific Ethanol announced that it will restart production at its Madera, Calif., plant on the heels of higher ethanol sales and the reversal of a hefty year-ago loss into a healthy $0.54 per share profit. By comparison, Wall Street had been forecasting a $0.01-per-share loss. Pacific Ethanol has certainly surprised investors to start the year, but keep in mind that the price it's receiving per gallon is actually lower than it was last year. Until we see consistent results, it's probably best to keep your expectations tempered.