This has basically the case in BC since 1941; an official Liberal/PC coalition until 52 when they ran separate and then the SoCreds won. From then till 96 the SoCreds were the defacto anti-NDP coalition party. Now were back to the days when the right is split, just in two not three
Up until Horgan-Eby, BC had class polarization more in line with Britain and Australia than North America. Politics was defined as "free enterprise vs. socialist." The BC NDP has been transformed into a big-tent center-left party not all that different from the federal Liberals. Today nobody except a few right-wing cranks thinks the BC NDP are a bunch of socialists hellbent on destroying free enterprise (and those cranks feel exactly that way about the LPC too).
Meanwhile, there's too much of a difference between the establishmentarian center-right on one side and the right-wing populists and ideologues on the other to all be in one party, particularly in the age of populism and post-truth politics.