Im currently living in a country with a multiparty parliamentary system. All of the various political parties here, however, are owned by a few wealthy families. A multiparty system may be necessary for democracy, but its not sufficient by itself. So long as the said political parties rely on plutocratic sponsorship, then there is always only one party, even if theres a hundred of them.
If we really had a true democratic system we would have more independent parties in the debates. We wouldn't be stuck with two guys who have been chosen for their ability to help the upper class. We wouldn't have two sides of the same coin. It's stupid.
We have a one party state with two factions that essentially are the same.
The parties have become too polarized in recent decades, with Republicans leaning far to the right and Democrats far to the left. This polarization hinders bipartisan cooperation and leaves the majority of Americans unrepresented. Most U.S. citizens fall somewhere in the middle of the political spectrum and cannot properly align themselves with either of the two existing parties in the United States.
My parents have been voting for about decade now and they have been voting for democrats. People in our country should have more than just republican and democratic to choose from. The voter may abstain from voting if the two choices are not to the voters liking. A third party gives the voter another option to select from that may better represent the personal preferences and morals the voter holds.
Third parties subtract voters and power from their closest major party. For example, if the Green Party became significant and held many seats in the senate and the house, then formerly Democrat voters would begin voting for the green party. This would split liberally minded voters and representatives in two, allowing Republicans to gain power. Overall, Green Party (or any other third party voters) would be at a loss, despite having their ideas more specifically represented, they would have less overall influence. As an actual example, in situations like this, the opposition to a major party often funds that party's closest third party in order to divide their opponents.