The problem is that we each have a limited number of votes.
Indeed, that is the problem. People voting for questions they think are on- or off-topic is perfectly appropriate, regardless of what the current "score" is. If you have 200 people following a proposal and the majority votes a single question on- or off-topic, then you should probably be more confident in its on-/off-topicness than if only 10% of them vote for it - I think that's fairly obvious, but the system needs to stop fighting it.
As the jjnguy notes, screwing with folks' ability to vote on stuff is just as likely to skew the results as it is to accomplish anything useful. Also, it could make somewhat-controversial questions appear to be more controversial - one with 20 who think it's on-topic and 90 who think it's off-topic would appear to be deadlocked if votes are capped at 20.
Solve the root problem, solve the symptom...