The ongoing Trump investigation, wearing out the broad public?

We know what Trump repeatedly says, and this is that there is no investigation of him.  We watch as his son is interviewed by interested parties, a member of his campaign staff has pleaded guilty to a crime, his short lived National Security Adviser Flynn who played a prominent role in his campaign has pleaded guilty to a crime as well, a campaign manager(Manafort) and an advisor(Yates) have been charged with crimes, and it continues.  Of course Trump is at the center of all of this.  While obvious, so far Trump is right that there is nothing pinned directly on him.

A concern here is that all of this may deflect attention from an unequivocal impeachable offense that will most likely happen given time.  Impeachment and then conviction would be a serious event for the country.  That is an understatement.  If attempts are made to step into that maelstrom with a case that is not precise and as completely indefensible as possible, the public's appetite for going through this could be wasted.  Mueller is persevering, but will his investigation fall short?  If so, does Trump gain an aura of invincibility?  That's a worry.