I just outranked The White House for their own content.
Demonstration of effect hidden content has on rankings. This includes tabs, accordions and other common content expansion mechanisms.
A page that shows visible content by default, tends to perform better than a page that hides the content.
To prove a point, I found a prominent page on The White House website that uses hidden content.
Page URL: https://www.whitehouse.gov/get-involved/join-us/
I copied that content and put it on Dejan Marketing home page and please note that I've read their copyright policy which states that "government-produced materials appearing on this site are not copyright protected."
Here is a screenshot from these Google results an hour later:
On reader's request, we've now switched to hidden content and have caused the drop in rank:
We'll follow up by switching between the visible and hidden content for a number is cycles to see if the gain and drop is consistent with each change.
If it's important don't hide it.