Most single winner districts are extremely predictable in that one can predict with very high probability who will win an election long before the actual election occurs.
This certainly occurs with gerrymandered single winner districts and is possibly inherit to single winner districts that use the conventional plurality voting system (vote for one, whoever gets the most votes wins).
Only a few factors can lead to a very solid prediction of who will win. Incumbency is one such factor. Incumbents almost never lose.
Take the 2006 midterm elections as an example. This is viewed as ‘a great change election’. In that election over 94% of incumbents remained in power. And this, indeed, was a shake-up. Normally an incumbent will win an election 98% of the time.
To see just how predictable elections are, consider the projections that FairVote makes in it’s Monopoly politics report. They make their predictions 2 years ahead of the elections and have had an accuracy rate of 99.8% in projecting winners in the 1,613 races the called between 1996-2004 (for 552 races they did
not make predictions but instead labeled these races as competitive or vulnerable). The only data that they use in predicting the winner for a district is the results from recent federal elections in the district and the incumbent’s party and seniority.
So incumbents win 98% of the time and 75% of US legislature elections are predictable with 99.8% accuracy more than one year ahead of the elections. In other words, we don’t really have a two party dominated political system. Instead each voter is effectively dominated by one party.
An open question:
The ‘one party’ article references the ‘political oddsmaker’ site by Ron Faucheux. However, the link to it is broken. Is this still online? What is the link?