Shigeru Ishida had beaten Economic Security Minister Sanae Takaichi in the final round of the Liberal Democratic Party election on Friday.

Japan’s benchmark Nikkei 225 index tumbled nearly 5% early Monday after the country’s ruling Liberal Democrats chose Shigeru Ishiba, a former defense minister, as the next prime minister.

Ishiba prevailed over hardline nationalist Sanae Takaichi in a run-off vote in what was one of the most unpredictable Liberal Democratic Party leadership elections in decades.