Stock indexes swung above and below the break-even line Tuesday, ending the day in the red. The Nasdaq and the S&P 500 shed 0.3%, while the Dow Jones industrial average trimmed 0.2%. The small-cap S&P 600 dropped 1.3%. Volume in the stock market today increased sharply on both major exchanges. A battle continues around the 50-day moving average lines. The Nasdaq and the S&P 500 closed just under their respective lines.