Is this a factor investors should take seriously, or is it just entertaining to argue about?
The presidential election is typically not enough to make major investing decisions in itself, however, based on how highly inflated the market is right now, it makes sense to be precautionary.

Is this unusual election year likely to make the markets break with past patterns?
The thing that makes this election year cycle unusual is the fact that the stock market has been so highly inflated artificially to begin with. That’s the reason to be leery, not just because of the election itself.

How will the general economic conditions in the U.S. and around the world change things this year?
If you believe the fed and wall street is in the tank for the democrats then more than likely they will prop up the stock market until the election to help a democrat get elected.
If the market is down, this would lead more people to vote for a republican.

Is it a time for investors to be cautious, perhaps putting cash on the sidelines?
I believe now is a great time to be cautious, but again, not simply because it’s an election year, but because of the fundamentals of the economy and the bubble we are sitting on.