A Malaysian reform party led by two former cabinet ministers faces a new test ahead of a crucial state election after one of its founders was sidelined over an alleged religious morality offence, threatening its appeal to voters disillusioned with the country’s political establishment.

The controversy surrounding former environment minister Nik Nazmi Nik Ahmad could undercut Bersama’s promise of delivering a different kind of politics in next month’s Melaka poll, analysts say – although some...