Under First-Past-the-Post, power is awarded to the leading candidate (not the majority one.) This can lead to vote splitting: when many similar contenders divide the vote in fragments allowing the other side to win. This can produce the opposite of what people want:
1996 BC election: In BC, the Liberals represent right-leaning voters (there’s no major conservative party.) When Reform ran in 1996, right-leaning vote-splitting let the NDP win a fake majority with less votes than the Liberals. Results: NDP 38%, Liberals 40%, Reform 9%.
1993, 1997, 2000 federal elections: During this time, two right-leaning parties — Reform and PC — split the vote producing perpetual Liberal majorities. The right-of-center parties were forced to unite under the Conservative banner to end the unfair advantage the Liberals got.
2011 federal election: After the conservative parties united, the center-left was fractured into three parties: Liberal, NDP and Green. This three-way vote splitting allowed Harper to win a false majority on 40% of the vote, when a vast majority was strongly opposed to that outcome.
Federally, things have become so ridiculous parties are now "micro-targeting" votes because key ridings are decided by a small number of voters. This is the opposite of democracy. The majority is supposed to determine the will of the people, not a tiny minority.