I don't know the extent of a downturn, but, the market is very weak internally. Many of stocks that led the rally have already pulled back to levels that are more than just a correction.
An example is Gilead Sciences. It peaked at about 120 and is now ~75. I can point to many others.
I took a cash position at the beginning of 2016 and haven't regretted it for a second.
The market has been pretty docile for the past few months, IMO, because of uncertainty about the election. After that's done, I'm expecting fireworks.