Nigel Wright “will not be shying away from any questions” when he takes the stand Wednesday at Sen. Mike Duffy’s trial, a source close to Stephen Harper’s former chief of staff tells CTV News.

The source also said that Wright “takes the duty of the (court) process very seriously” and intends to “demystify” any lingering questions from the public and the media.

Wright is expected to testify about his secret $90,000 payment of Duffy's allegedly improper living and travel expenses in 2013. Wright wrote Duffy a personal cheque and has said that Harper had no knowledge of the arrangement.

Harper has also denied knowing anything about Wright’s $90,000 cheque to Duffy.

Court documents quoted Wright as saying in a 2013 email that “we’re good to go from the PM.”

But at a campaign event this weekend, Harper said: “The words you’re quoting are not my words. They’re somebody else’s.”

Wright intends to explain to the court what the “good to go” comment meant, the source said.

The RCMP laid 31 charges against Duffy. Three of them are related to the $90,000 payment: fraud on the government, bribery and breach of trust.

Harper will be far away from Ottawa this week as Wright takes his turn as the star witness at Duffy’s trial. The Conservative leader’s campaign is heading to northern Canada.

Harper repeated on Tuesday that he had told Duffy, a former Conservative senator, that he “should repay his expenses.”

“I was told that he was going to repay those expenses, and we were all told he had repaid those expenses,” Harper said at a rally in Markham, Ont.

With a report from CTV’s Katie Simpson and files from field producer Philip Ling in Ottawa