Josh Campbell is a CNN analyst covering national security issues. He previously served as a supervisory special agent with the FBI, special assistant to the bureau's director, and is writing a book on recent attempts by elected officials to undermine the rule of law. Follow him on Twitter at @joshscampbell . The views expressed in this commentary are his own. View more opinion on CNN.

As a former investigator, I see the Cohen affair's most damning revelation to be the President's knowing and longtime association with a crimina l, not that the criminal in question pleaded guilty to a crime that directly implicates the President of the United States (as disturbing as that is). Given the evidence, Trump can no longer plausibly deny that he was willing to cross the line and work with Cohen to break the law.

After being sentenced on Wednesday to three years in federal prison for committing crimes against the United States, Cohen insisted he was "taking full responsibility" for his past actions. Despite his emphatic declarations of remorse and contrition , Cohen shouldn't be surprised if the American people respond to such claims with a giant dose of skepticism. The same hesitation should be applied to any denials from Trump.

Cohen is not some upstanding pillar of the community who accidentally ran afoul of the law. Rather, he's a crook who finally got caught, and is now facing justice. That he has decided to cooperate with special counsel Robert Mueller is noble but should not overshadow Cohen's role in committing serious campaign finance violations.

The Cohen case gives us a unique window into Trump's mindset, character and view of the rule of law. To protect his electoral chances, Trump and Cohen appear to have paid off women in exchange for their silence about alleged affairs with Trump, in the process breaking campaign finance laws.

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However, Cohen's crimes (though many of the counts he was convicted on were not connected to Trump) have implications for Trump that extend far beyond the payment of hush money. They largely discredit any claim Trump might try to make about his ignorance of additional potential crimes carried out by others in his inner circle. The Cohen crimes speak volumes about the kind of people Donald Trump surrounded himself with.

Indeed, Michael Cohen was not some random attorney retained by Trump to make election liabilities go away. Rather, he was the business mogul's long-time lawyer and fixer.

If you or I were attempting to carry out a crime, we would likely have a very hard time finding other people to join our effort. Most of us don't associate with crooks.

Apparently, not so with Trump. When faced with an embarrassing situation that might threaten his candidacy, all he had to do was turn to a close confidante in his orbit. Put simply, he had a go-to guy who could help him violate the law, if necessary, to deceive the American voters in an effort to attain the highest office in the land.

The reason this is so important is because there are larger legal issues looming for President Trump regarding his campaign's alleged ties to Russia and the integrity of those in his inner circle. We know Trump has closely associated with at least one criminal -- Michael Cohen -- so how are we to know there weren't other crooks in the candidate's midst?

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We also know the President lied to the American people about his knowledge of the payment of hush money and the role of one of his top lieutenants in the affair. He has similarly denied any wrongdoing by his associates as it relates to the ongoing Russia collusion investigation. However, knowing he apparently colluded with Cohen to break the law and then lied about it, how are we to believe we are not being deceived about Russia as well? The President has simply exhausted all credibility.

One final significant aspect of the Cohen sentencing is the fact his case signals the first instance of someone in Trump World pleading guilty to something directly related to Trump. Thus far, the Mueller probe has brought down several key associates -- Paul Manafort, Michael Flynn, and George Papadopoulos, to name a few -- but none of these convicted felons was charged for actions involving the President.

Manafort was convicted of financial fraud and for deceiving investigators. Flynn lied to the FBI about phone calls he had with the Russian ambassador. Papadopoulos pleaded guilty to lying to the FBI about his efforts to obtain dirt on Hillary Clinton. In all three cases, Trump enjoyed a modicum of deniability as it related to him personally.

Cohen is a different story. The revelations this month in court all but list Trump as an unindicted co-conspirator in a plot to defraud the people of the United States.

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