Kevin Horner of Charles Schwab outlines key support levels for the S&P 500 (SPX), including the 50-day moving average, and flags potential defensive positioning if it breaks. He highlights D.R. Horton (DHI) as a breakout candidate from a nine-month range. Horner also points to strength in Dollar Tree (DLTR), which is nearing four-month highs and stands out within the staples sector.