Charles II made sure he had the majority of supporters in parliament through a combination of blackmail, persuasion, and bribery. By using blackmail, he could gather information on individuals and use it to manipulate them into supporting him. Through persuasion, he could convince others to align with his interests and gain their support. Additionally, he resorted to bribery, offering financial incentives or favors to secure the loyalty of parliament members. By employing all of these tactics, Charles II ensured that he had a majority of supporters in parliament.