Err, no. Contrary to some of the posts herein, there is no requirement that a reasonable person would believe the defamation. The requirement is that a reasonable person would interpret it as defamatory–as opposed to taking it ironically or as praise or whatever. In practice, that distinction is often elided because the difference is pretty slippery. But quite outlandish statements can be defamatory as long as their outlandishness doesn’t suggest they are made ironically or as exaggeration or the like.
Well, from a nonlawyer’s perspective, whether a reasonable person would believe the defamation is relevant to establishing damages. For non-per se defamatory statements, at least. Though perhaps you can just explain nominal damages.,
Correct. If people don’t actually believe it, then it’s hard to show that your reputation has been mangled.
Similarly, if your reputation on that subject is already shitty, it’s hard to show damages. The NYT’s lawyer noted this in his response to Trump’s threat to sue over the accusations of sexual assault.
There are still criminal libel laws in the US that are enforced.
The low bar for these kinds of things was set with 2 cases between G. Gordon Liddy and John & Maureen Dean.
Liddy quite explicitly described Maureen as a former call girl, that the Watergate break-in was engineered by John to cover this up and a number of other disgusting allegations.
The first case, in 1992 was handled quite oddly by the judge. Liddy’s insurers offered a settlement but it was turned down because the Dean’s wanted their day in court. The judge threw out the lawsuit with prejudice! Whoa.
Liddy continued to make his horrible allegations, grounds for a new trial in 2001. That resulted in a hung jury. Effectively another win for Liddy.
These cases illustrate how incredibly difficult it is to win defamation cases when politics are involved.
In particular, hung juries are a serious problem. The defendant gets to pick judge or jury. Picks jury, of course. At least a few supporters of the defendant will sneak thru selection by lying. They’ll bottle up things during deliberations. A “win” for the scuzzball.
Another point to remember is that truth is an absolute defense against libel. Now, I’m not saying that all of Trump’s defamatory statements are true, but at least some of them are bound to be.
I can’t tell if the OP is serious or not.
Also, in order to be slander or libel, the statement must deal with factual assertions. Opinions can never be objectively true or false and cannot be the subject of libel.
Saying that Hillary has “hate in her heart” is one of these. We can’t actually take a scientific test that shows that her heart is nearly 98% hate-free.
Slut, whore, and trollop are more difficult. In a sense, they are opinions (calling a woman a whore does not typically mean that you are literally stating that she exchanges sex for money). And although RNATB is correct that accusing a woman of being “unchaste” is libel/slander per se, truth is a defense to this, and unless it can be shown that the woman in question never engaged in fornication or adultery, then it becomes a matter of opinion: how much sexual activity makes a woman a trollop or a slut? There is no accepted definition for this.
And, again, we are talking about remarks uttered in a political campaign. It would be chilling towards free speech if a candidate has to worry about being sued when responding to issues of public importance. The “actual malice” standard should apply in that a person cannot make a verifiably false statement regarding a fact that he knows to be false, and it has a measurable damage to the person so slandered or libeled.
The collection of examples makes the question pretty ridiculous IMO. There might be cases where lying politicians (the idea Trump is unique in this respect is itself ridiculous) who went close enough to the line wrt actual slander/libel standard for a public figure (target) that a case might be made in a real court. But not these.
How could you establish the known factual falsity of a claim a public figure is ‘crooked’* or ‘has hate in their heart’? Perhaps you shouldn’t have worried about an overly long post and included this factual evidence for each case including those two. 
On the MSNBC one it’s an untruth one might prove the speaker knew to be, but the problem would be proving that it defamed NBC. Would the discovery process show no cases where NBC outlets (and not unique to them) actually did quote public figures out of context including with selective editing of videos? I doubt it.
*it obviously can’t be slander/libel of Clinton to say some general group is trying to swing the election in her favor, so I guess you must mean the epithet is slander/libel
Trump’s defense is simply that he was hurling abuse, which is protected under the 1st amendment. Most terms of abuse are not meant to be taken literally. If they were, then so much as being called a jerk would be actionable, and accusations of carnal relations with your own mother would most certainly be.
Didn’t Jerry Falwell sue “Hustler” over that last one. If I recall, he lost because a fake ad with Falwell drinking bourbon and talking about having sex with his mother was clearly parody/satire.
As others have noted, it is HARD for a public figure to sue for libel or slander in the USA. Trump would have a much harder time in Europe or even Canada.
But under the Sullivan decision, a public figure who’s been assailed verbally by Doald Trump cannot successfully sue for libel or slander unless he can prove
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Trump said something false
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Trump either KNEW it was false or made no attempt to verify what he said
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He said these things solely for the purpose of hurting the other person’s reputation.
It would be very tough for any of Trump’s rival candidates to prove those things.
Campari not bourbon
“I was hurling abuse” is not a defense.