The Tories hold the most seats in the upper chamber and would be able to use that leverage to slow down legislation, force amendments or push their own private member's bills up higher on the Senate's agenda.
That was what the Liberals did when Stephen Harper was first elected in 2006. The Tories were the minority in the upper chamber and had to negotiate with the Liberal majority to get legislation like the Accountability Act passed into law.
"We're going to deal with them just like they dealt with us when they were the majority," said one senior Conservative senator, who spoke on condition of anonymity because the caucus had yet to discuss its next steps.
Most negotiations, the senator said, will be civil, although Conservatives may not freely give their votes on legislation.
"I don't have any responsibility to pass Liberal legislation."
A senior Liberal in the Senate likened it to guerilla warfare: the Tories will pick their spots to score political points, but avoid all-out war that could hurt the reputation of the Senate.
Another Conservative senator said an acrimonious Senate would only reinforce the popular narrative that the place is packed with partisans who are not interested in critically reviewing legislation, the upper chamber's traditional role of sober second thought.
There are 22 vacant seats in the Senate; another opens up in February with the impending retirement of Conservative Irving Gerstein, the party's top fundraiser. By the end of 2016, there will be 26 vacant seats as Conservative Michel Rivard and Liberals Celine Hervieux-Payette and David Smith hit the mandatory retirement age of 75.
Filling all those seats with Liberal-minded senators would give Trudeau more than half of the 105 seats in the Senate.
Trudeau has promised to create an advisory panel that would make recommendations on Senate appointments in a bid to remove some of the partisanship from the upper chamber.
Trudeau didn't put a timeline on when that promise would be kept when he was asked about it during a news conference earlier this week.
Nor did he say what he would do about getting his government's agenda through the Senate, including having a Liberal point man in the upper chamber.
"These are part of the conversations that we'll be having with Senate leadership to ensure that both our government can function well in both Houses, but also that we have the kind of thoughtful non — or less — partisan approach from the Senate that I think Canadians expect," Trudeau said.
That has left long-time members of the Senate wondering what will happen next.
Usually a change of government means that parties swap government and opposition offices in the Centre Block. This time, everyone is staying put for now: Liberals in the Senate have yet to hear from Trudeau about what role they will play, given they were all turfed from Trudeau's caucus last year.
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