A sea of red-clothed Malaysians of various ethnicities loudly made their way out of the Persada Johor International Convention Centre into the darkening twilight.

Nearly 10,000 grassroots members and leaders had spent their Sunday at the Pakatan Harapan convention in Johor Bahru, where the coalition intended to unveil its direction for the upcoming elections.

After serving nearly four years as part of the government, the gathering...