Having 3 or 4 popular parties would not cause a problem. There are governments all around the world that work tieh 5,6,7,even 8 popular parties that all get a significant portion of the vote. No "mandate" means no one is feeling safe to be pushy and they must work harder at working together, or else they'll be voted the hell out.
And I like to give people a little more credit than saying that keeping track of 3 or 4 viewpoints instead of 2 is too difficult for them
