As he has done so many times before, Nigel Wright took to the streets of Ottawa early this past Monday morning.

Running his daily 20 kilometres, back in the city where he dedicated some of his life â€” the city he left when it was revealed he had given suspended Senator Mike Duffy $90,000 to pay off his allegedly fraudulent expense claims.

Wright will testify Wednesday in Duffy's criminal trial in Ottawa as a Crown witness.

Sources tell CBC News that the former chief of staff for Prime Minister Stephen Harper is not stressed about his testimony. Wright  has been preparing with lawyers over the past days, and while he will acknowledge in his testimony that he made a mistake, his goal is to come out of the courtroom with his reputation intact.

That may prove difficult.

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Nigel Wright is expected to be cross-examined about his communications with Prime Minister Stephen Harper in connection with the $90,000 payment made to Mike Duffy. Harper has said he was not aware of the payment. (Chris Wattie/Reuters)

Wright is a key figure in the Crown's case against Duffy and the charge of bribery. Prosecutors have suggested Duffy was the "instigator" of the deal. But given that Wright co-operated extensively with the RCMP by handing over hundreds of emails and speaking to police at length, the first days of questioning by the Crown may not be as much of a challenge.

But his testimony is central to their case. It was Wright, after all, who provided the RCMP with hundreds of emails detailing how the Duffy spending scandal was being managed and contained inside the Prime Minister's Office. It was also Wright who provided the RCMP with Duffy's personal diaries, which allowed investigators to piece together key details about where Duffy was when he was claiming housing and living expenses.

'A political problem'

Wright will face tougher questions when Duffy's lawyer Donald Bayne steps up to the plate.

Bayne telegraphed in his opening statement how he planned to depict Wright — as the leader of a "small group," directing "a concerted strategy to deal with a political problem."

Bayne will try to show that Duffy was forced to "capitulate to the pressure of the small group."

The cross-examination is expected to take days. And if Bayne's previous tactics are any indication, it will be thorough and demanding.

And as he has done in the past, Bayne will use every opportunity to drag politics into the courtroom.

That possibility should worry the Conservatives. 

Emails already released by the RCMP show how deeply concerned the Prime Minister's Office was with the potential fallout from the Duffy investigation. 

There were days of talks and negotiations around how to make Duffy repay the money.

At one point, Wright was close to signing off on a deal that would have had the Conservative Party Fund pay for Duffy's expenses, then believed to be $32,000. 

Wright emailed the PMO lawyer, Benjamin Perrin, writing, "I do want to speak to the PM before everything is considered final." An hour later, he followed up with another email, "We are good to go from the PM."

That phrase has, to this day, never been fully explained. What was it exactly that Wright took to the prime minister? And what did Harper then approve as an acceptable solution?

Harper has said he was not aware that Wright subsequently paid for Duffy's expenses when the Conservative Party refused to pay the larger tab. But Wright may well be asked, at what point did he choose to stop telling Harper any further details?

These are all points that Wright could clarify, possibly revealing other issues Harper will have to face during an election campaign. 

The Conservatives have said they believe the damage by Duffy has been done.

They are about to find out if they are right.