In a statement today, White House press secretary Sarah Sanders called Cohen a "disgraced felon," noting his past lies to lawmakers. "Sadly," the statement says, "he will go before Congress this week and we can expect more of the same. It's laughable that anyone would take a convicted liar like Cohen at his word, and pathetic to see him given yet another opportunity to spread his lies."
In his testimony, Cohen is expected to detail his motives for having helped Trump and for now coming clean, the person familiar with the matter said. He will offer "very specific details" - some of which have not yet been made public - about arranging the hush-money payments at Trump's direction, the person said.
Cohen also is expected to "provide more detail about his lies to Congress" and address in some capacity a BuzzFeed News report asserting he told Special Counsel Robert Mueller's office that the President directed him to lie, the person said.
The Special Counsel has disputed that report, though Cohen has not said anything about it publicly.
Cohen is expected to present records of Trump's finances and recall alleged instances "where Trump used high numbers for his purposes, such as getting on the top 10 wealthiest people on the Forbes list, and low numbers, when it came time to paying real estate taxes," the person said.
Cohen's allies hope he could become this generation's John Dean - President Richard Nixon's White House counsel who famously testified to the Senate about Nixon's involvement in the Watergate scandal that ultimately led him to resign.
Whether Cohen's testimony will be as impactful depends on the questions he is asked, the new facts he is able to present - and the evidence he has to back up his assertions.
Here are 20 questions lawmakers could ask Cohen that might shed new light on the investigations swirling around Trump.
1) You pleaded guilty to lying to Congress about a possible Trump Tower project in Moscow. In a memo for your sentencing, your lawyer wrote, "Furthermore, in the weeks during which his then-counsel prepared his written response to the congressional Committees, Michael remained in close and regular contact with White House-based staff and legal counsel to Client-1." (Client-1 refers to Trump.) Who are the "White House-based staff and legal counsel to Client-1" that you remained in contact with, and what instruction did they give you about your testimony?
Though Cohen has already admitted to lying to Congress about the Trump Tower Moscow project in an effort to diminish the ongoing inquiries into Trump's possible ties with Russia, it remains unknown if others in Trump's orbit knew he planned to do so or, worse, directed him to do so.
Cohen's defence lawyer offered only this tantalising hint during the sentencing process about Cohen's contact with "White House-based staff and legal counsel to Client-1." Cohen could say who those people are, what they knew and when they knew it - which could have significant implications for them.
2) BuzzFeed News reported that Trump directed you to lie to Congress, and that you told the Special Counsel as much. Describe any conversation you and Trump had about your testimony. Did he direct you to lie, and did you tell that to the Special Counsel's office?
If Cohen were to testify that Trump explicitly directed him to lie to Congress, that would implicate the President in a plot to obstruct justice. At the same time, however, it would raise doubts about the credibility of the Special Counsel's office - which has disputed that is the account Cohen gave them.
At the very least, Cohen could help clear up the mystery surrounding the controversial BuzzFeed report and detail what interactions, if any, he had with Trump about his testimony. Cohen's lawyer has written previously the lie "sprung regrettably from Michael's effort, as a loyal ally and then-champion of Client-1, to support and advance Client-1's political messaging." But was Cohen lying merely because he knew what Trump wanted, or because Trump told him to do so?
3) Do you believe Trump obstructed any investigation, and do you have evidence to prove that?
Particularly key would be whether Cohen has evidence that hasn't been made public yet.
4) Were you ever offered a pardon in exchange for being silent?
If Trump dangled a pardon to dissuade Cohen from cooperating with law enforcement, that could constitute obstruction of justice.
5) Can you provide more information about the frequency and substance of your conversations with Trump about the Trump Tower Moscow project after January 2016?
These conversations are important because Trump repeatedly said he had no business dealings in Russia. He tweeted in July 2016, "For the record, I have ZERO investments in Russia," and told reporters in January 2017 that he had no deals there because he had "stayed away." Cohen's describing his knowledge of a Trump Tower Moscow project could further expose those claims as false. Cohen has admitted he lied to Congress when he told lawmakers discussions about the project ceased after January 2016.
6) Can you provide any further information about the frequency and substance of your discussions with Trump family members regarding the Trump Tower Moscow project?
In his plea, Cohen admitted that he briefed Trump family members about the project, but no other details were offered.
7) What campaign official did you talk to about possible travel to Russia?
Cohen's plea says he "asked a senior campaign official about potential business travel to Russia," but it does not say who that official is.
8) Please describe any contact you had with the Russian government about Trump Tower Moscow or other topics during the 2016 campaign.
Cohen has described some limited interaction he had with the Russian Government about the Trump Tower Moscow project, but this would give him an opportunity to offer more detail on it and other interactions.
9) You have repeatedly denied the allegation contained in the so-called "Steele dossier" that you travelled to Prague during the campaign to meet with Russian operatives. Here today, under oath: Did you or anyone else associated with Trump travel to Europe during the campaign to meet with anyone associated with the Russian government or acting on its behalf?
Cohen has repeatedly and publicly denied this claim, which appears in the controversial dossier that levels lurid allegations against Trump, but his doing so under oath would be notable. Cohen, more than most, knows the consequences of lying under oath.
10) To your knowledge, was Trump ever informed by his son Donald jnr or anyone else before his son took a meeting with a Russian lawyer in June 2016?
Trump has repeatedly said he did not know that his son met with Russian lawyer Natalia Veselnitskaya during the campaign, and any information Cohen has to contradict the President's assertion would be significant.
11) Do you believe that Trump or anyone associated with his campaign coordinated with a Russian effort to interfere in the US election?
Cohen has previously insisted he is unaware of any evidence the Trump campaign coordinated with Russia. Any suggestion to the contrary now would be a bombshell.
12) According to court documents, two Trump Organisation executives were involved in 2017 with approving your reimbursement for money paid to adult-film actress Stormy Daniels before the 2016 election. The two executives agreed to describe monthly payments to you as legal services, the documents say, though you were no longer working for the company as a lawyer. Who were those two executives, and do you have reason to believe they knew at the time that that description was not accurate?
Court documents do not name the executives. Their knowing the description was inaccurate might connect them to the wrongdoing to which Cohen already has pleaded guilty.
13) How many times did you discuss payments to Karen McDougal and Stormy Daniels with Trump before and after the 2016 election? Describe each of those conversations to the best of your memory.
McDougal, a former Playboy model, and Daniels each alleged affairs with Trump - which Trump denies. By answering this question, Cohen would be connecting the president in more detail to his own wrongdoing, as he has admitted the payments violated campaign finance law.
14) Did you ever discuss payments to McDougal and Daniels with other members of the Trump family? With other campaign officials? Describe those conversations.
Answering this question would connect Trump's family members to the crimes to which Cohen has pleaded guilty.
15) According to AMI's non-prosecution agreement, you met with AMI publisher David Pecker and a member of the Trump campaign in August 2015 to discuss how AMI could assist the campaign by buying and burying negative stories about Trump's relationships with women. Was the campaign member Trump? Please describe what occurred at that meeting.
AMI is the parent company of the National Enquirer, and signed a non-prosecution agreement to avoid being charged in connection with the crimes to which Cohen has pleaded guilty. Cohen would be implicating Trump in connection with that wrongdoing if he places Trump at this meeting and describes any role he played. The Wall Street Journal previously reported that Trump was at the meeting.
16) AMI's agreement with the government also indicates that Pecker agreed at that meeting to keep you apprised of any such stories when they arose. Please describe each instance you can recall where Pecker reached out to discuss a possible negative story regarding Trump? Are you aware of other instances during the campaign when you helped arrange for people with potentially negative information to be paid for their silence? Please describe any such instances.
Cohen pleaded guilty in connection with making hush payments to two women, but having worked for years as Trump's fixer, it is possible he is aware of other stories Trump wanted kept out of the media.
17) What role, if any, did you play in the March 2016 AMI stories alleging, without evidence, that Senator Ted Cruz had engaged in extramarital affairs? How about in the AMI story that suggested Cruz's father could have played a role in assassinating President John F. Kennedy?
These are two specific stories that targeted a Trump political opponent.
18) Stormy Daniels has said that in 2011, when In Touch magazine was preparing to publish a story about her alleged affair with Trump, a man threatened her and her infant daughter in a parking lot in Las Vegas. Do you believe that episode occurred, and were you involved in any way?
A lawyer for Daniels has alleged this episode occurred and even released a sketch of a possible suspect, though law enforcement has never accused anyone of a crime in connection with the claim. Cohen has previously denied any knowledge of this alleged episode.
19) In January 2018, you produced a letter purportedly from Daniels, denying an affair with the President. Did you discuss that statement with the President before writing and releasing it?
As with many of the questions above, Cohen's answer would speak to Trump's possible involvement in trying to downplay or dispute allegations of marital infidelity.
20) You have admitted that you lied the last time you testified before Congress, and you will be going to prison for that. Why should we believe you now?
Republicans are likely to raise significant concerns about Cohen's credibility, with good reason. For his explosive assertions to stick, he will need to produce evidence that supports what he says.
