On the eve of the resumption of the Mike Duffy trial and in the midst of the second week of election campaigning, the leaders of the three main parties fielded questions about the Senate expenses scandal and what they expect to hear when star witness Nigel Wright, the prime minister's former chief of staff, testifies this week.

Conservative Leader Stephen Harper avoided getting into the specifics when he was asked at a campaign event in Markham, Ont., whether he knew of the party's plan to cover Duffy's expenses, which were initially thought to be $32,000, with money from the Conservative Party fund.

He avoided answering the question directly and instead repeated his past assertion that he had always told Duffy to repay "those expenses that were taken from the Senate that we thought were not proper."

'We have taken appropriate actions to make sure people are being held accountable.' - Stephen Harper, Conservative leader

"I was told he was going to repay those expenses, and we were all told he had repaid those expenses," Harper said in response to a reporter's question. "When I learned that was not true, I made that information public, and we have taken appropriate actions to make sure people are being held accountable, and that is what is happening."

Harper also said it's common for the party to "provide some support for colleagues who have legal issues." The Conservative Party did cover more than $12,000 in legal fees for Duffy, but those were not part of the $32,000 in Senate expenses.

Harper mum on Wright firing/resignation

According to emails quoted by the RCMP in court documents, the prime minister's chief of staff Nigel Wright indicated he received the go-ahead from Harper on the plan to cover Duffy's expenses with the party fund. The emails are expected to be a key focus of Wright's testimony when he takes the stand at Duffy's trial this week.

"We are good to go from the PM," Wright wrote in a Feb. 22, 2013, email to Benjamin Perrin, the prime minister's former adviser and legal counsel.

The plan was abandoned when Duffy's illegitimate expenses ballooned to $90,000, and Wright paid the money out of his own pocket.

Wright was later fired or resigned — although Harper on Tuesday did not clarify which when asked by a reporter.

Mulcair accuses Harper of flip-flopping

Wright's testimony also came up at NDP Leader Tom Mulcair's campaign stop in Mascouche, Que.

"I do find it interesting that Mr. Harper has decided to try to hide out in the North Pole during the Duffy trial," Mulcair said, referring to the fact that Harper is taking his campaign north this week just as the trial resumes.

Mulcair also criticized Harper's comments from earlier in the week about whether he did or didn't tell Wright that he was "good to go" when it came to covering Duffy's expenses.

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NDP leader Tom Mulcair was asked about the upcoming testimony of Nigel Wright during an election campaign stop at a prefabricated home factory in Mascouche, Que. (Ryan Remiorz/Canadian Press)

"This week, he denied saying "good to go" in the House of Commons, he did everything but deny it," Mulcair said, responding to a reporter's question about Wright's upcoming testimony.

"On a whole series of subjects, Mr. Harper has said one thing and its opposite in the Mike Duffy affair, and as you know, you can't say one thing and its opposite and both of them be true. A lot of that is going to be catching up with Mr. Harper this week. He can run, but he can't hide."

'[Wright testimony will] bring out something that we have known for a long time: the only thing that matters to Mr. Harper is to stay in power at all costs.' - Justin Trudeau, Liberal leader

The Duffy trial also came up at Liberal Leader Justin Trudeau's campaign stop. Trudeau told supporters gathered at his campaign office in the Papineau riding of Montreal on Tuesday that Wright's testimony will be a "sad spectacle" that will "bring out something that we have known for a long time: the only thing that matters to Mr. Harper is to stay in power at all costs."

"It's important to remember how the Senate saga began," Trudeau said. "After promising to Canadians that he would not appoint a single senator if he was elected, Mr. Harper broke that promise 59 times," he said, referring to the Senate appointments Harper made during his two terms as prime minister.

Harper said in July that he would put a moratorium on new Senate appointments.

Liberals promises non-partisan appointments

Trudeau promised that if the Liberals were elected in the Oct. 19 federal election, they would introduce an "open, non-partisan, merit-based process" of appointing senators. 

"As [Liberal Party] leader, I took decisive action removing Liberal senators from my caucus because partisanship and patronage need to be removed from the Senate," Trudeau said.

But Trudeau stopped short of saying he would abolish the Senate if his party were elected on Oct. 19, saying such a promise would be reckless since abolishing the upper chamber would require a constitutional amendment that some provinces would never agree to.

Trudeau vows new Senate appointments system1:36

He called out Mulcair, who has said he would work to have the Senate abolished, for making promises that are "cynical and dangerous" and which he can't deliver.

"My priority will not be to reopen the Constitution. The absolute priority will be to create economic growth," Trudeau said.

He told supporters Senate reform was one part of the Liberals' three-pronged plan to make government more open. Denouncing Harper's government as "the most secretive, divisive, hypersensitive government in Canada's history," Trudeau said the Liberals would also make government information more accessible and give MPs greater freedom to represent the interests of their ridings without having to worry about toeing the party line.

When asked directly about what questions he wants answered in this phase of the Duffy trial, Trudeau avoided answering and said only that what the trial will confirm is that Harper's government is "solely and uniquely focused on its own well-being and its own survival and its own grip on power" rather than service to Canadians.