Oft repeated phrase, mistakenly attributed to Winston Churchill, true author unknown. Regardless, it's quite popular:
"If you're not Liberal when you're 25, you have no heart. If you're not Conservative when you're 35, you have no brain."
It appears that it is not just I who believes that it is not unusual for the young to dabble in liberalism.
Liberals during Churchill's time vs. ours are very different creatures and therefore his comment is no longer applicable. It is surely, however, quite a consolation to some, which is probably the reason it is still so often repeated.