But the half dozen or so senators who've chosen to the attend the event in Montreal this week say they've been made to feel thoroughly welcome.
Rival parties have been trying to make hay with the presence of senators at the gathering, suggesting it proves Liberal Leader Justin Trudeau's move to boot them out of caucus was a meaningless gimmick.
The NDP has been handing out cards with the faces of all 32 Liberal senators arrayed in rows like numbers on a bingo card, asking: "Can you spot them all?"
At least seven of the 32 have put in an appearance so far.
Internal Conservative party documents, leaked to the Toronto Star last week, indicated the Tories had been planning to snap photos of senators at the Liberal convention to post online.
But James Cowan, leader of the now separate Liberal Senate caucus, said Friday there's no reason senators shouldn't attend the convention.
"I don't know how it would embarrass Mr. Trudeau. He made the right decision to separate the caucuses. I've thought that a long time," Cowan said in an interview.
"I think senators need to be more independent. It doesn't mean they can't belong to a political party," he added, noting that the expelled senators are all still active members of the Liberal party.
Trudeau's surprise move last month was aimed at restoring the Senate to its intended role as an independent chamber of sober second thought.
Under the party's constitution, senators are still technically members of the national caucus, although the leader has discretion to decide who is allowed to attend caucus meetings. They are also entitled to a number of special privileges, including automatic delegate status at party conventions.
The deadline for proposing amendments to the constitution at this convention had already passed by the time Trudeau gave senators the boot. Hence, their privileges will continue until the next convention in 2016.
However, the party's national board has proposed a "sense of the convention" resolution, seeking after-the-fact grassroots endorsement of Trudeau's decision to evict senators from national caucus.
"I'm not here to spoil anybody's party," said Sen. Jim Munson, who is attending the convention to champion a resolution on a national autism strategy.
"The reception has been warm. I've even got some hugs from a number of delegates."
Sen. David Smith, who headed national Liberal campaigns under Jean Chretien, said he's been coming to Liberal conventions for more than 50 years.
"To me it's family," he said in an interview.
Smith said it's "baloney" to suggest the presence of senators at the convention undermines Trudeau's decision to cut caucus ties in a bid to make the Senate less partisan. Senators will no longer be involved in national election or fundraising campaigns, he added.
"Free at last, free at last from fundraising so I can't say that I feel bad about that," he joked.
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