Is this an ad hominem (guilt by association)?

Without starting a political debate, I want to ask about a particular part of the U.S. Presidential election. Many people used the endorsement of Donald Trump by David Duke, a former KKK leader, as an attack on Donald Trump's campaign. Is this a form of the guilt by association ad hominem?

There are two forms I can think of that I heard commonly:

David Duke is a racist.
David Duke endorses Donald Trump.
Therefore, Donald Trump is a racist.

and

David Duke was a leader of the KKK.
David Duke endorses Donald Trump.
Therefore, you should not vote for Donald Trump.

Thanks in advance!

This argument has annoyed me because of its fallaciousness. Yes, it is a clear ad hominem, guilt by association. For decades, the KKK has openly endorsed candidates. They have to (should) choose someone, so they choose the candidate that is best for their cause. This can only tell us which candidate's policies are most in line with the KKK's. But those who buy this argument mostly use it as just another reason why one should not vote for Trump—I would guess that nobody made their decision based on this (beside, perhaps, KKK members who did vote for Trump). Thinking critically, one would have to weigh all the pros and cons of a potential candidate and make the best decision based on big picture. Yes, I agree that having the KKK support Trump over Clinton does say something about the direction of Trump's political views, but it does not justify calling Trump a "racist" nor is it reason not to have voted for Trump.

The only fly in the soup here id that Trump did not disavow the endorsement.

@ Frank Dugan “The only fly in the soup here id that Trump did not disavow the endorsement."

False. Trump did disavow per e.g., www.youtube.com/watch?v=k. . .
One could quibble with Trump's initial equivocation during the interview with Jake Tapper, in which he professed not knowing David Duke and his specific association with the KKK (I was not please with his tepid response) but he did clearly disavow a day or so later. There is more that can be said about this, generally. (See my reply to Bo)

@ Bo Bennett

I agree with your analysis completely, and would add that IMOP, it took a fair amount of personal courage to voice this accurate, logical view in these turbulent times.

The nature of this fallacy while technically ad hominem, I think is more precisely defined by its subset: “Guilt by Association” (which you also mentioned).

Over the last seventy or so years we’ve had a couple of highly prominent ‘Guilt-by-Association’ plagues: 1.Nazism and 2. McCarthyism.

I believe the scope of these association ‘plagues’ has exerted great influence on our contemporary culture. I further assert that existence of the “guilt by association” fallacy that may be ascribed to each is not cut & dry, but individual/situation specific.

Though beyond the scope of this brief reply, I believe these examples deserve greater scrutiny in terms of what defines a true G-B-association fallacy, and what may alternately constitute acceptance (and furtherance) of the immorality of the respective Groups, though such support may involve only a passive role.

It should also be noted that Trump likes painting walls white..........wall racist??

In addition to the conspicuous logical fallacy (Guilt by Association) concerning Trump, David Duke and the KKK, I believe there to be a lot of misinformation being propagated (or assumed) by members of this forum concerning this issue.

I contend the following:

1. There was never a formal endorsement of Donald Trump’s Presidential Candidacy by either the KKK or David Duke. The most that can be said is that certain Trump platforms loosely coincide with the expressed interests of the aforementioned. The rest is hyperbolic extrapolation by a largely biased Media.
2. To the contrary, there is considerable evidence that Trump has had a long history of antipathy toward David Duke and the KKK. (You need to ‘dig deep’ for this as the Media refuse to acknowledge or present it.)
3. Trump’s actual ‘Disavowing’ of Duke and the KKK was a reaction to the false but widespread PERCEPTION that an endorsement (and strong nexus) were factually present. Untrue, but a political necessity.

Sources:

Source of purported, actually faux endorsement of Trump by KKK
http://www.vocativ.com/372496/ku-klux-klan-endorses-donald-trump

WAPO misleadingly citing this (above) cover story as a Trump endorsement by KKK
https://www.washingtonpost.com/news/post-politics/wp/2016/11/01/the-kkks-official-newspaper-has-endorsed-donald-trump-for-president/

Lengthy article providing analysis and context of Trump’s ALLEGED support for David Duke & KKK (See Sect III).
http://slatestarcodex.com/2016/11/16/you-are-still-crying-wolf/

Denial by David Duke that he endorsed Donald Trump
http://davidduke.com/dr-david-duke-the-zio-media-lies-i-have-not-endorsed-donald-trump/

I am quite open to receiving any WELL –DOCUMENTED arguments that may prove me wrong.