There are many aspects to this investigation that is evident, first and foremost being that Mueller intentionally inflated the investigation far beyond that of Russian collusion in regards to election activities. Once Mueller decided Manafort's conduct of many years prior to the election was to be re-investigated (in prior years the FBI had wire-tapped him more than once, apparently finding nothing actionable) we all knew the original purpose had changed to "get Trump's associates and then Trump because of who they are". The motive was so transparent that Rod Rosenstein had to create the paperwork in August of 2017 to RETROACTIVELY expand and justify Mueller's conduct that had already taken place.
And it is evident that because there is no substantive "collusion" with the Russians, Mueller raided Trump's attorney's office as a direct assault on Trump's personal (and lurid) history and his business.
So now that investigation has zero point zero relevance to is original purpose, the anti-Trump hysterics are "indicting a ham sandwich", using lawfare to achieve political ends. So let's look at this latest transparently political ploy:
1) It's not a criminal campaign finance law violation to pay for anything campaign related using your own funds. To the degree that Cohen paid the money for Trump (re Stormy Daniels), as his attorney he merely floated an expense, representing Trump, to be reimbursed by Trump. Case closed.
2) In the case of the National Enquirer's purchase of the exclusive rights to Karen McDougal's story, Trump did not pay for it. If the purchase of an exclusive is illegal because it is intended to "influences an election" then all such stories in elections are "in-kind contributions", whether they are published or not. What a paper does with a story always influences an election, and is often meant to do so. In other words, its called freedom of the press. Trump did not direct a felony because it was not a felony.
3) And its even unclear if the law being used is being properly understood. The law is for no other purpose than to deter corruption (bribery of the elected) and to check the "undue influence" of economic interests. Yet, neither the Trump-Cohen expenditures have anything to do with "corruption" or the undue influence of economic interests. Candidates that fund themselves directly or indirectly are being influenced by themselves, and those accused in this case of in-kind contributions are not motivated by bribery, but personal support.
4) Bradley A. Smith, former chair of the FEC (and one of the few leading authorities on election law) has stated:
https://www.wsj.com/articles/stormy-weather-for-campaign-finance-laws-1523398987
All of which leads to the absurd catch 22: if this expense would not exist but for the campaign, then it must be paid by campaign funds (of which he can contribute as much as he likes). Then, of course, if Trump had directed the campaign to do so, he would be accused of using campaign funds for private hush money and could be impeached for that.
Needless to say, this is what happens when law is ssstttttrrrreaaachhhhed to the point of incoherency.