Nate Silver speculates on why the GOP tidal wave could actually be a tsunami: 1) Once voters start pulling the R lever for one race, it will become habit; 2) Tea Party draws in “unlikely voters” that pollsters are missing; 3) The notion that undecided voters tend to break against the incumbent; 4)”Scott Brown Effect” — voters in blue states use this election as a once-in-a-lifetime chance to send an R to Congress; 5) some likely voter models based on past voting histories are overrating the propensity of Democrats to vote.