In presidential politics, timing is everything.

It is all about being the right candidate for right now. What you have or have not done is less important than how your sensibilities align with the cycle.

And every election is different, which makes efforts to graph the lessons of previous elections onto a current one a somewhat futile and fruitless exercise. Yes, there are some things that change slowly like demographics, but the mood of the electorate is not one of them.

Every electorate is shaped by and responds to not only the wind at their backs but also whatever is blowing in their faces. Should an incumbent be unseated or saved? Is it an election for change or for continuity?

The problem is that voters figure out the true contours of a race only once voting and caucusing begin. The race at the beginning — the leading candidates and the most resonant issue — is often unrecognizably different from the race at the end.