A common cognitive bias in political analysis is what Daniel Kahneman calls the availability heuristic: the tendency to focus on recent or familiar examples as opposed to the broader course of history and the richer volume of precedents.
There is some risk of this in Massachusetts, where the Democrat Martha Coakley lost a special United States Senate election in January 2010 to the Republican Scott Brown. The state is holding another special Senate election in June, in which the Republican candidate, Gabriel Gomez, is drawing comparisons to Mr. Brown, and Republicans are hopeful that they can win again.
The problem with using the 2010 race as a precedent is that it may have been an outlier. [cont.]
Nate Silver, FiveThirtyEight (NYT)