Levin, still seeking his first PGA Tour win, carded 75 to tie for fourth with compatriot Daniel Summerhays (69).

CNN: STORY HIGHLIGHTS

Summerhays also reached as low as 7 under before falling back with a bogey on No. 9, but it was Horschel who separated himself with his late flurry.

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The American closed with two birdies to sign for a 68 and take a handy lead over compatriots Daniel Summerhays (69) and Charley Hoffman (67) as well as Australia's Steven Bowditch (69).

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