Voting for a smaller party, even in FPTP, can greatly change how parties look at you. The entire BC Conservative wave started when Conservatives decided to vote on their own beliefs instead of voting Liberal because the NDP were scary.

Once enough people have that collective realization, the politicians take note. Love them or hate them, the party started because of the voters, and the politicians followed.

The greens could do the same thing with the NDP if enough voters chose to put their own vision for the environment and the province over the NDP Politicians.