Seth B. Waxman, a partner at the Dickinson Wright law firm in Washington, served as a federal prosecutor in the United States Attorney's Office for the District of Columbia and has worked as a criminal defense lawyer in Washington and New York. The opinions expressed in this commentary are his own. View more opinion on CNN.

(CNN) Recent revelations in memoranda filed by the government against Michael Flynn, Michael Cohen and Paul Manafort describe even more widespread and troubling contacts with the Russians. However, since the inception of the Mueller investigation, President Donald Trump, his lawyers, legal pundits on both sides of the aisle, and everyone in between has either claimed or conceded that "collusion" is not a crime.

President Trump has tweeted, "Collusion is not a crime . ..." Rudy Giuliani told Fox News , "I have been sitting here looking in the federal code trying to find collusion as a crime. ... Collusion is not a crime." Jay Sekulow told The New Yorker, "For something to be a crime, there has to be a statute that you claim is being violated. ... There is not a statute that refers to criminal collusion. There is no crime of collusion."

Having worked as a federal prosecutor for 13 years in the Clinton, Bush and Obama administrations, I can report that the President and his lawyers are wrong. Collusion is a crime. The federal criminal code says so. The federal bribery statute - - 18 U.S.C. § 201(b)(2)(B) -- makes it a federal crime for a public official to "collude" in a fraud on the United States. More specifically, the federal bribery statute expressly states that a crime is committed when a public official "directly or indirectly, corruptly demands, seeks, receives, accepts, or agrees to receive or accept anything of value ... in return for ... being influenced to ... collude in ... any fraud ... on the United States."

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Merriam-Webster's Dictionary defines collusion as a "secret agreement or cooperation especially for an illegal or deceitful purpose," exactly the focus of special counsel Robert Mueller's investigation. Committing fraud on the United States means to impair or obstruct the lawful functions of a government agency. The Federal Election Commission and the Department of Justice are responsible for disclosing to the American people any foreign influence in the American political system and US elections.

What does this mean for President Trump? The answer has three steps: (1) if Trump sought, received or accepted from the Russians "dirt" on Hillary Clinton, a promise to assist in building Trump Tower Moscow, or anything else of value; (2) in return for being influenced to engage in a secret agreement with the Russians to influence the 2016 US presidential election without the FEC, DOJ, and American people knowing; (3) then Trump and anyone who knowingly and intentionally participated in those acts is guilty of illegally colluding under federal bribery law -- a crime that carries a 15-year maximum prison term

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In the social media case, Mueller alleged that the Russians illegally impaired and impeded the FEC's and DOJ's ability to disclose to the American people the Russians' social media influence in the American political system and 2016 US presidential election -- the same type of "collusion" allegations Mueller may well be able to lodge against Trump as a public official under the far more powerful federal bribery law. Mueller may also use this approach to go after and flip the President's son, Donald Trump Jr. and son-in-law, Jared Kushner, among others.

Federal bribery charges can also apply if Trump accepted things of value from the Russians in exchange for a promise to perform a future official act, such as reducing or eliminating US sanctions against Russians; this is known as the "official act" prong of the federal bribery statute . In contrast, the "collusion" prong of the federal bribery statute covers a broader range of conduct and need not involve official government acts.

Another important wrinkle in federal bribery law that could potentially prove devastating to Trump is the fact that federal bribery law covers conduct beginning on the date Trump was "nominated" for office on July 19, 2016, or even earlier, on May 26, 2016, when Trump was officially informed he won the necessary 1,237 delegates to become the presumptive Republican nominee for president. Thus, Trump will not be able to defend his conduct on the ground that he first became a public official when he was sworn into office on January 20, 2017.

Historically, candidates for office were not subject to federal bribery law. However, in 1962, the law was extended to cover candidates because Congress realized the law as previously written failed "to provide against the bribery of persons in anticipation of their assumption of public office. ..." And, "[t]hose who assume public office under a corrupt commitment ... may thus be afforded a loophole."

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To remedy this loophole, Congress concluded that the law "should be extended to prospective public officials, in order to cover cases in which the promise, solicitation, or illegal consideration passes prior to entry on official status. ..." The Mueller investigation may prove the 1962 Congress particularly wise.

Collusion has a common-sense understanding. But federal bribery law and the Mueller investigation may put illegal "collusion" into the history books. President Trump and his associates should certainly be worried.