Hornish led 114 laps in his second career Nationwide victory, but needed a strong finish to outrun Busch, the hometown driver who won the Nationwide race last week in Phoenix.
Hornish and Busch both went aggressively after the final restart with seven laps to go, with Busch briefly nudging ahead before Hornish reclaimed the lead with five laps left.
Hornish got clear of Busch and finished comfortably in a caution-filled race.
Pole sitter Brian Vickers finished third, with Trevor Bayne fourth and Elliott Sadler fifth. Travis Pastrana came in 10th, four spots ahead of Dale Earnhardt Jr.
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