On April 22, 81-year-old Toshihiro Nikai, the 12-term Liberal Democratic Party Lower House member from Wakayama Prefecture, marked 1,359 days as party secretary-general. He is now the second-longest serving person in that position in the 65-year history of the LDP, following Kakuei Tanaka, a former prime minister. If he is still in the post come September, he’ll be the longest-serving.

LDP's secretary-general is de facto the most powerful person within the LDP after the president, who doubles as prime minister when the LDP is a ruling party. Since the party’s founding in 1955, 12 men who held the post have become prime minister. Here’s a look at the office and some of those who served in it.

What is the role of the LDP secretary-general?