The S&P 500 index Monday afternoon shed all of its early gains to briefly turn negative as the stock market pared firmer gains. The S&P 500 index was trading at break-even levels at 2,728, most recently. Declines in industrials, down 0.3%, financials, telecommunications and real estate were among the worst performers among the S&P 500’s 11 sectors. The Dow Jones Industrial Average , which had been boasting a triple-digit rise, and within six points of reclaiming its psychologically significant level at 25,000 at its intraday peak, was up just about 62 points, or 0.3%, at 24,894, with a decline in shares of McDonald’s Corp. delivering the stiffest headwind to the price-weighted average. Meanwhile, the Nasdaq Composite Index was up 11 points, or 0.2%, at 7,412, also off its session high.