Hahaha, who do you think is the simplistic one here? Do you think for one minute the PAP will quietly give up their rule if they got voted out? Do you know how much corruption shit, conflict of interest, net worth of the ministers and PAP elites etc. will be dug up after the oppo takes over? They have so many skeletons in the closet that all of them will be looking at jail time.
If you want to know what has to happen, just look at similar situations where a long time despotic ruler or party have been in power, and where they appeared to have total control of all aspects of the country, and than see how they lost their power. A good example is the KMT and Taiwan. Marcos and the Phillippines is another example, or Libya and Gadhafi. The Taiwan case is the best example.