HILTON HEAD ISLAND, S.C.—With a second-round 65—jump started by a smooth 5-under-par 31 on the front nine at Harbour Town Golf Links—Luke Donald took a 1-stroke lead at the midpoint of The Heritage and moved one step closer to the top of the World Golf Rankings. Donald, who can move from third to first in the rankings if he wins Sunday at Harbour Town Golf Links, posted seven birdies to a lone bogey on Friday to edge Garrett Willis for the lead at the halfway point of what could be the last PGA Tour event at Harbour Town.

Englishman Luke Donald leads by a shot at the midpoint of The Heritage. He can ascend to the top spot in the World Golf Rankings with a victory on Sunday. Photo by Reid Spencer

Donald finished at 65-67—132. Willis followed his opening 64 on Thursday—the low round of the tournament so far—with a 2-under-par 69—133. Willis birdied his final hole Friday, the par-4 ninth, to move one shot ahead of Camilo Villegas, defending champion Jim Furyk, Jason Day and Chad Campbell, all tied for third at 8 under par.

Given reporters’ questions and frequent reminders on social media, Donald has found it hard to forget that the No. 1 ranking is a possibility.“Well, I’m playing well, so I guess it’s always in the back of your mind,” Donald said after the round. “It’s hard to get away from, knowing that with Twitter and Facebook and the media and everything, you obviously know what’s at stake.

“But again, if I manage to go and win, No. 1 is just the outcome… I can control where I hit the golf ball, and, hopefully, I’ll give myself a good shot at it come Sunday.”

The world rankings are calculated to reward consistence excellence over a two-year time frame.

“If you look at the system, it means you’re performing the most consistently over a two-year period,” Donald said. “It would certainly be an honor and a great achievement to accomplish.”

Asked whether he thought he was the top player in the world, Donald smiled.

“Not yet,” he said.