This is an assumption you have made and it isn't always true.
they represent a minority opinion
The most important roles of minor political parties has been to give the voters and option outside of the 2 major parties. Minor political parties have altered the outcome of some of elections.
they cant take away enough voters away from the major parties
I believe it is because the minor party, itself, cannot vote in the major party direct elections.
They take votes away from major parties candidates.
Even though it may seem like minor parties don't have much of an effect on politics and elections, minor parties can actually make enough difference to change an election. Minor parties rarely win elections but are actually necessary to politics. The small amount of people that vote for minor parties could potentially cost enough for a major party to lose an election to the other major party. For example: If an election is 50/50 between Democratic and the Republican parties and 10 percent of the Democrats decide to vote for a minor party it would cost the Democrats the election. Hope this makes sense! Good luck!
The advantages to proportional representation are that minor parties also get seats in the government. In a proportional elections, the people do not need to feel like voting for a minor party is a waste of a vote. This leads to a multiple parties who need to form coalitions to create a majority vote.
third parties are also called minor parties
third parties
Minor parties take votes away from the candidates of other parties.
Just that - minor parties, seldom of political significance.
third parties