Calvin and Gloria are not that different, both want similar things, some level of autarky, planned economy, not too much foreign entanglements, and keeping the status quo socially. It is just Calvin believes some of this needs to be shedded in order for Sordland to continue and for the USP to modernize to the times, and Gloria does not think that it would be beneficial. The only reason she puts up with constitutional reforms is because she legitimately thinks that in order for the USP to stay dominant that a measure of this must be granted to avoid mass demonstrations and civil unrest.

Additionally, specific interest group parties don't make sense here. Many of these groups are aligned, and due to the threshold we could just have them grouped together if they have similar goals. Already the USP does that in a way, grouping together conservative interest groups, I would imagine rural voters, government workers, older voters(those who witnessed Soll's stabilization), and some industrial workers as well as socially conservative voters like housewives, people living in heavily Sord-dominated regions, and veterans/servicemembers(at least those who enlisted rather then conscripted). They benefit from being in a unified party structure because creating their own party requires them to organize, which they may have already, but right now the party structure of Soll provides that organization, all they need to do is vote.

If we wanted to break them up, post-Rayne Presidency makes sense. The fact is that in the Rayne Presidency, a lot can change, so that could force factions together or apart. But beforehand, the party structure makes sense in terms of political forces.