@Ernest Bywater
I suppose you could really upset the major political parties by getting a law change that a candidate must have at least 1 vote over 50% of the eligible voters in that constituency. Thus if too many don't vote you can have a vacant seat because they didn't get more than 50% of the eligible voters supporting them.
Not workable for a great many reasons. Primarily, because it would destroy any rights of third parties.
In a great many elections, nobody gets over 50%. A great many Presidential Elections in the history of the country have had this result. In 1992 Bill Clinton won with only 42% because it was a 3 way race. Arnold became governor of California with only 43% once again because it was a race with a staggering 135 qualified candidates.
And in a great many cases, doing that would literally throw the decision to fill the seat right into the hands of the Mayor-Governor, or the Legislature of the body that oversees that seat. You are essentially creating a system where it could be gamed and a political party could do everything in it's power to prevent anybody from winning, therefore giving say the Governor the power to put into that office whoever they want until the next election.