The situation is similar in Canada - a significant number of people would support the NDP, but they're viewed as a spoiler. In my parent's riding, for instance, 55% of people voted for the two left-wing candidates, so the seat went to the right-winger who got the remaining 45%.

A concerted effort to consolidate votes behind the Liberals gave us Justin Trudeau, a do-nothing neoliberal whose hobbies include brownface and giving indigenous people's land to oil companies.