On Saturday thousands of yellow-shirted protestors will take to the streets of Kuala Lumpur and two other Malaysian cities to demand the resignation of Najib Razak, the country’s prime minister. Mr Najib has been on the back foot since July, when a report in the Wall Street Journal suggested that payments of nearly $700m had found their way into his bank accounts shortly before a closely fought election in 2013. Mr Najib firmly denies wrongdoing; party colleagues say that he received a legal political donation from an unnamed wealthy Arab family. The rally’s organisers—a coalition of civil society groups called Bersih—reckon he has wriggled out of a proper investigation. Since 2007 they have held several rallies demanding reforms that might strengthen Malaysia’s weak democracy. In 2012 police dispersed thousands of protesters with tear gas and arrested about 500. This weekend’s demonstrations could go the same way.