It's happened before... a few times.

Ironically once with Richard Nixon... who would of been impeached but not for that.

And he ordered the stopping of the investigation of himself!

He got censured though.  So did Andrew Jackson for basically doing the same thing with his secretary of the treasury.

There is constant claims, and actually pretty decent proof to show that crimes persued tend to be based largely on who is president.  Right down to which groups get prosecuted and investigated... not just the type of crime.

Both of the last administrations have lawsuits against them for unfairly poltiisizing the justice system and covering up for their side.

Either way, this rarely becomes public because, as said, the president usually gives prefrences and directions on what to prosecute where, and is given a heads up about ANYTHING sensitive.  As can be seen by the above, where he tells people what to prosecute, and what not to. (As previously he specifically said he wasn't going to let the justice department raid drug farms and users that are illegal under federal laws.

And I mean really.  This guy used a copyrighted photograph... of a guy who there exists thousands of pictures of.

The POTUS should really be public domain.

Although really it's kind of a moot point.  Since the president could always just pardon them.

And I mean, pretty much every president spends his last few days in the whitehouse pardoning all of their friends who got in trouble.

I thought it was going to be a false advertising charge...

Hey now, all those posters said was hope.  They didn't actually promise the president would do anything.  Just that he'd make people believe he would for a while.