Many of the 60% must have some kind of ties to the gov't e.g. civil servants, GLCs, teachers,... Easily threatened with with a lose of a job, lost of privilege,...etc
All the PAP has to do is to pick a few as examples & use them as examples to scare everyone else into line.
The 40% aren't as easily cowed since they are just "lesser mortals" with nothing to loose.
As more people loose their jobs to foreigner, there will be more who are willing to vote for the opposition.
Many of the young voters fall into the 2nd category. As things stand now there isn't much of a future for them.