The Senate has just voted for a major shake-up of how members of the Red Chamber align themselves by allowing nine or more members to form a caucus, a substantial break from tradition that has historically seen the place organized along party lines.

Members of the Senate adopted a key recommendation of the modernization committee's report — released last fall — which removes the requirement that a caucus only be formed by those who are members of a political party registered under the Canada Elections Act.

Thus, in theory, there could now be a proliferation of caucuses along regional lines, something that has been favoured by Peter Harder, the government's representative in the Senate, in the past for organizational purposes.

There could also be the creation of more narrowly-focused caucus groups, like senators who support environmental causes, or the military, an Indigenous or women's caucus. The possibilities are nearly endless as long as there are at least nine senators who agree to band together, and their group is created for parliamentary and/or political purposes, requirements that are not overly stringent. (A senator, however, cannot be a member of more than one caucus.)

I do think the wind has gone out of the sails of this idea of regional caucuses. - Conservative Newfoundland Senator David Wells

The change is a personal victory for Harder, and his reform agenda, as he has sought to dislodge the Conservative and Liberal duopoly in the Senate.

"I think it's a victory for the Senate. This is the first major, permanent adjustment to the Senate rules and procedures coming out of the modernization committee," Harder said in an interview with CBC News. "I just think its important for senators to be given the framework ... to form affinities [and] I don't have a road map or expectations or a design here."

Harder said regional caucuses could form but he isn't pushing for that type of division now, adding the process will "play out organically."

When asked if there was demand by senators within the chamber to form new caucuses, Harder said yes. "Why else would it have been accepted by the Senate?"

The motion directs the Senate rules committee to now formalize the changes, and then requests the internal economy committee — which effectively governs the chamber and adjudicates complaints — to draw-up budgets for these prospective new caucuses, to help hire staff for "secretariats" and pursue research projects. The motion was adopted by a voice vote, so it is not clear how much support it had from the existing parties.

The change comes amid a charm offensive of sorts by Prime Minister Justin Trudeau, who met with some senators last night to thank them for their efforts to usher government legislation through the upper house.

Trudeau also met with Nova Scotia Senator Stephen Greene who was booted from the Conservative caucus Tuesday because of his openness to the Senate reform championed by Harder. He will now style himself as an "Independent Reform" senator and could now, theoretically, entice other senators to sit with him in a caucus.

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Conservative Newfoundland and Labrador Senator David Wells, the party's caucus chair in the Red Chamber, and a member of the modernization committee, said he is broadly supportive of the new rules as long as the chamber does not morph into a bureaucratic body devoid of politics. Retired Liberal senator Jim Cowan also feared such changes would turn the place into a "$90-million debating club."

Newfoundland and Labrador Conservative Senator David Wells says he supports rule changes to what constitutes a 'caucus,' but he wants the chamber to maintain its political character. (Garrett Barry/CBC)

"While we might not always like to admit it, senators are still politicians and generally in politics you align with political philosophy you don't necessarily align by [regional] boundary," the Newfoundlander said in an interview with CBC News. "I do think the wind has gone out of the sails of this idea of regional caucuses.

"I'm a partisan now, I'm a Conservative, and I will remain partisan but I will also remain true to my directive of giving fair consideration to all legislation," Wells said.

Trudeau up-ended the status quo after he kicked Liberal senators out of the national caucus in 2014 while promising to strip partisanship from the chamber by insisting on the appointment of Independent members. The "government" caucus in the Senate is just three members, Harder, deputy representative Senator Diane Bellemare, and a liaison, Senator Grant Mitchell, who performs some of the roles a whip.

Because he faced a significant list of vacancies when he assumed office, Trudeau has been able to appoint a large number of new senators in a relatively short time through a "merit-based" application process. In the last year alone, 27 senators have been appointed and a further 11 senators will be appointed by the year's end (or 38 out of a total 105 senators).

Virtually all of these new appointees have joined together with a handful of other senators — who left the Liberal or Conservative caucuses for various reasons — to create the Independent Senators Group (ISG) led by Alberta Senator Elaine McCoy, who acts as its leader or "convenor." (The caucus definition change also formally brings the ISG under the Senate's rules.)

Wells said while the new senators were appointed as Independents, they have since realized it is beneficial to caucus together to share money, staff and other resources.

"They have quickly become political, and they are, by and large, supportive of the [Liberal] government's agenda," he said. "These are still appointments by a partisan process that ends with the prime minister of the day making the final decision."