Lahiri's cards of 70-67-67 have broken a string of record for Indians at Majors. Placed tied eighth as of now, he is bidding to become the first Indian to win a Major and only the second from Asia to win a Major after YE Yang's effort at the 2009 PGA Championships.
Lahiri is at nine-under 207 and six shots behind the leader, Jason Day of Australia. Lahiri, who shot sub-par scores in each of his first three rounds at The Open last month, repeated the feat at Whistling Straits, to make it two in a row.
His spectacular 67 in the second round saw him tied-fourth, the best an Indian player has been placed at that stage at any Major.
His 67 is also the best-ever round by an Indian at any Major and bettered cards of 68, once each by Jeev Milkha Singh (2008 PGA), Lahiri himself (2012 British Open) and Shiv Kapur (2013 British Open).
Interestingly, Jeev had shared the lead after the first round at 2008 PGA Championships, but was tied eighth after second round, tied seventh after third round and finished tied ninth at the end of the tournament.
Lahiri is playing his seventh Major, of which six have come in succession. He has made the cut in four and his best has been T-30 at British Open this year. Last year he played the PGA Championships for the first time and missed the cut.
Lahiri, only the second Indian to make Top-50 of the world, has won seven titles in Asia, of which two - Malaysian Open and Hero Indian Open - were co-sanctioned with European Tour.
He is also in line to become the first Indian to play for the International Team at the President's Cup, an event held every two years between United States and Rest of the World (minus Europe).