This might be one of those scandals that's really bad if you think it through and understand its implications, but could appear on first glance to be too esoteric to really make an impression on the electorate. Don't let that happen. This is very big and very bad.
In essence: When Hillary became Secretary of State, she agreed to a policy insisted upon by the Obama Administration that before the Clinton Foundation would accept major gifts from foreign governments, she would give the State Department a heads-up and an opportunity to raise any concerns they might have.