Damn good question. The answer is, you can’t. Period. This circus was out on as a grasping for straws attempt to unseat someone they don’t like. They do that with everyone, though. It’s just much easier to yell down joe public. A little harder with a sitting president, especially when you know you have nothing and have to make shit up as you go along.
I hate to sound so partisan (literally.... I despise posting political stuff of any kind on facebook), but obstruction of justice is barely a crime.
It's a catch-all. It's something they use to charge people they don't like or can't get on other charges. It's like "disorderly conduct." It can mean fucking anything.
So of course they found no collusion with Russia but "couldn't answer" whether he was guilty of obstruction or not. They wanted him to be guilty of obstruction badly, but....
a) We don't even 100% know if a President can be charged with a crime at all, but the majority of evidence suggests he cannot.
b) Since the President actually is the one conducting the investigation, since he heads the department, the investigation necessarily rides on his whims and he can end it at any time. If you think the President committed a crime, impeach him, then investigate him when he's no longer in charge of the investigation. So we also really have no solid theory that the President can actually obstruct justice.
c) While it is possible to obstruct justice when no underlying crime was committed, surely the President's knowledge that no underlying crime had been committed weighs heavily in any analysis of this instance, since he can persuasively (and probably truthfully) argue that ending what he knew (and was proven to be correct about) was a witch-hunt outweighed any further chasing down rabbit holes by a biased Justice Department (ie, ending public corruption supercedes a phony investigation, so he had no attempt to obstruct "justice" - he intended to obstruct the miscarriage of justice. "Justice" is not defined per se by the statute). They cannot meet the "intent" aspect of the crime.
d) Even if, after all that, one still thinks that the President COULD be found to have obstructed justice, the level of which he is alleged to have obstructed (suggesting Comey end certain investigations but not demanding it, firing Comey but appointing another FBI director who continued the investigation, wanting to fire Mueller but not doing it, and tweeting mean things all the time), is superceded by every politician in office today literally all the time.... every time they refuse a subpoena or grease the wheels of an investigation or criminal process by pulling favors. It simply does not rise to the level of what obstruction of justice traditionally means in it's less "catch all" formats, ie, witness tampering or destroying evidence
It's a joke.
It's basically saying he exerted pressure on his own justice department (but never carried through an order demanding it), which he's legally the boss of and in charge of, to end an investigation that he knew would find nothing.... was obstructing justice.
