Yeah, if you want to break the law, a President can be impeached for events that occurred before he was President. But we can vote so it doesn’t matter.
They hate Trump with a passion, need to placate their increasingly insane base and they need to extract payback for Clinton's impeachment. They will impeach, its a certainty.
The one and only peaceful way to prevent that from happening is to vote to help keep the (R)'s in control.