Poulter made five birdies at the par-70 Phoenix Country Club to stand in a three-way tie with South Korea's Kim Kyung-tae and Japan's Toshinori Muto. Australia's Chris Campbell and Spain's Gonzalo Fdez-Castano were one shot back.
Defending champion Padraig Harrington of Ireland had a 2-under 68 and was tied for 10th place. Harrington beat Tiger Woods with a birdie on the second hole of a playoff last year. Woods, who won the tournament in 2004 and 2005, is not taking part this year.
Britain's Luke Donald had a 69 while American Brandt Snedeker shot an even-par 70.
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