I heartily agree with this:

Whatever similarities exist between the current campaign and ones in the past, they have no predictive value whatsoever. History does not repeat itself so precisely that it is possible to predict the future based on past analogies. That is a common, but sophist, way of understanding the world.

Every election season has its own peculiarities and concurrent dynamics. We currently have an out-going two term president who nevertheless is almost radioactive in terms of his popularity. There's this thing now called the internet, and it seems that just about everybody uses it. There's a black guy heading the ticket of a major party. Until very recently, the other guy running for president was continuously accused by his party's faithful of being a RINO. There's a really unpopular war going on, but no draft to really bring it home. Et cetera, et cetera, et cetera.

It seems that the main offenders of the analogy crime are the wise Washington pundit types. Most of the time, I think it's just a desire for people like George Will or Cokie Roberts to impress us with their supposed knowledge and readily apparent longevity. "This is reminiscent of '72. I'll never forget that time I was reporting from the floor of the Democratic Convention and George McGovern ... (see how smart and connected and wise I am? See? See?)"

But other times, I think that people commit the analogy crime in order to push a narrative while seeming "objective." When a pundit says McCain '08 is just like Dole '96, or Obama '08 is just like Dukakis '88, then how much of that analogy is objectively "predictive" and how much of it is actually a partisan dig? I'd say it's mostly the latter.