For "olor" just further down, I'd probably use whiff or stench (which works well with air, IMO).

And for pasa desapercibido, maybe that's hard to miss more than that's hard to ignore. Or make it negative- hard not to pick up on, hard not to detect, that few miss/fail to detect, etc.

More literal, perhaps easier to fit with the part that follows.

that is / are hard to ignore.

Vibration, feeling, touch, connotation... may work in the context?

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Note added at 4 hrs (2017-07-07 00:41:10 GMT)
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Looking at all the answers, and the original text, TD and DT, (TD = Tricky Dick), seem to be bond, just by the acronym: TD - DT... and that could be very poisonous, as in Terminal DDT...

Not to be frivolous, but to me, the "halo" (2. m. Círculo de luz difusa en torno de un cuerpo luminoso., per DRAE) that "connects" both figures, has a lot of "aureola", ("air" in way) that surrounds them.

I am not an expert on PR, far from it, but not really knowing what is cooking in the wings, the attempt to identify TD with DT, is of course an orchestrated black PR campaign against DT.

In other words, as the Old English goes "not all the gliSters is gold", by the same token, not everything that smells is shhhh... "¡shave and cream! Shave every day and you always look keen..." As the old song went.

At this point, I would even think of something like "identified by their public persona", that is "united" or "identified" by their image, face, public face, character, personality, identity, self, front, facade, mask, guise, exterior, role, part...

"However, there is a mystical yet undeniable bond uniting Richard and Donald."

This rendering captures the supernatural connotation of a "halo" uniting the character and destiny of two men whose service as president is separated by more than four decades.



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Note added at 34 mins (2017-07-06 21:03:15 GMT)
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Or, perhaps better, "bond between" instead of "bond uniting."

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Note added at 42 mins (2017-07-06 21:11:17 GMT)
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And perhaps "fatal bond" would work better than "mystical bond" to reflect "unidos por un halo."

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Note added at 2 hrs (2017-07-06 22:49:52 GMT)
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Thinking about this further, I think that "destiny" could be a good fit for both uses of "halo" here.

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Note added at 5 hrs (2017-07-07 01:38:36 GMT)
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ERRATUM:
"Halo" is of course used only once in the posted extract of text. What I meant to write in my last comment was that I think that "destiny" can be used both to translate "halo" and to deal with the "olor de impeachment" that is later mentioned (given that impeachment is, according to the author of the piece, one of the bases of the shared bond between Nixon and Trump).

As 'kindred spirits' is often used to relate to two 'souls' that share a certain 'essence,' perhaps something like this would be an option.

I also like Robert's suggestion of 'bond,' while (his) 'mystical' also fits nicely. IMO

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Note added at 5 hrs (2017-07-07 02:01:35 GMT)
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Hi Tom: We all bring our background information to a reading, as our interpretations are filtered through cultural lenses. That said, I'm not so sure many, much less most, readers would make that (rather learned) connection. :-)

This might work.

The idea of a smell/air/aroma that isn't altogether positive/pleasant ... I think 'whiff' might work. It is usually followed by 'of' ' + noun, but here we don't want a noun afterwards, so putting 'a certain' in front of it makes it sound okay without, and using the word 'both' gives us the idea that the two men share it / have it in common.

Another option could be: 'both have a certain whiff about them'. Actually, I quite like this one.

I can't find exact example sentences, only ones with 'whiff of' + noun' and 'whiff of' + noun + 'about' + him/her/name (etc), but, as I said, I'm confident the inclusion of 'a certain' before the word 'whiff' makes it work.

The text refers a little later to 'olor', so ....

Suerte

same haze