Peter MacKay says he's getting a bad case of deja vu heading into this month's Conservative convention.

In an interview, the defence minister described his exasperation with a passionate debate on party leadership rules that turns up like clockwork at the party's conventions, which are held every two years.

"There's a bit of a refusal to accept the strong will of the party by bringing this forward time and time again," MacKay said in an interview from Brussels.

When MacKay and Stephen Harper agreed to merge the Progressive Conservative and Canadian Alliance parties in 2003, the PCs insisted that each riding would have an equal say in a leadership vote.

The idea was that regions with huge numbers of members, such as western Canada, could not swamp other areas of the country such as Quebec or Atlantic Canada, where riding associations are smaller. But some elements in the party would like the rules to be closer to a one-member, one-vote system. The NDP has such a system.

"Nobody can describe it as a unifying issue, " MacKay said. "It's divisive. It pulls at old affiliations and old fault lines and I don't think we need that."

Two proposals have turned up in the package of resolutions to be debated at the convention in Calgary starting June 27. One would give more weight to larger ridings in a leadership race, another would go to a straight one-member, one-vote system.

"Democracy is best served when members choose the leader and when leadership candidates seek support from and serve the membership," reads one resolution.

Idea defeated in 2011

The proposal was soundly defeated at the 2011 convention in Ottawa, as it was at three previous conventions. Minister of state Maxime Bernier and other Quebec MPs sided with MacKay, as did some party elders such as former Ontario premier Bill Davis and former finance minister Don Mazankowski.

But this time, with the convention in Calgary, a vote could theoretically be closer. Neither of the current proposals names the sponsoring riding associations. In the past, Immigration Minister Jason Kenney, Foreign Affairs Minister John Baird and Ontario MP Scott Reid have backed the change, with Reid emailing out materials on the issue in 2011. The sponsor ridings weren't named in 2011 either.

"I understand it's not being put forward openly and honestly because we're not sure who's doing it," said MacKay. Reid and Kenney were not immediately available for comment.

Fred Delorey, a party spokesman, said only that constitutional resolutions were put forward by four riding associations from two provinces.

For MacKay, changing the rules would represent a setback for the party. He said the current formula requires a leadership aspirant to reach out to the entire country to ensure victory, rather than relying on pockets of regional support.

MacKay refers often to the negotiations between the Progressive Conservatives and Canadian Alliance team to broker their merger.

"I felt very strongly about it then – so strongly, Stephen Harper would know, that our founding constitution would not have happened without this principle," he said.

MacKay, Bernier, Kenney and Baird are all names that surface as potential successors to Harper, although none of them have said they would seek the leadership.

D'Arcy Barker, a former member of the Canadian Alliance's national council, noted that the debate is not evenly split between former Progressive Conservatives and former Alliance members. He said he came around to the concept of the ridings all having an equal voice, arguing that it encouraged more long-term workers, donors and members.

"After '98, I thought the PC method was flawed," Barker said on Twitter. "After experiencing '03, I saw it built long-lasting party infrastructure."