KUALA LUMPUR, June 13 -- Two of Malaysia's wealthiest states are heading to early elections that have set the partners in Prime Minister Anwar Ibrahim's unity government against one another and handed him the first serious electoral test of his premiership since 2022.

Johor, on the southern tip of the peninsula and governed by Barisan Nasional, dissolved its state assembly on June 1. Negeri Sembilan, held by Anwar's own Pakatan Harapan, followed on June 4, with its vote set for August 1. Under Malaysian law, polls must be held within 60 days of a dissolution.

The two coalitions are uneasy allies. Pakatan Harapan and Barisan Nasional, bitter rivals for decades, joined forces only after the 2022 general election produced a hung parliament...