The political system will always revert to 2 major parties. That cannot change, it is the nature of the system.
I believe runoff elections would though. Currently if one party runs multiple candidates something like this happens:
Democrat 1 receives 33% of the vote.
Democrat 2 receives 33% of the vote.
Republican 1 receives 34% of the vote.
Democrats had two strong candidates with some differing views, and decided to let both candidates run so the people would have more of a choice. The result is that 66% prefer a Democrat but a Republican ends up in office.
(Spare me the "their both corrupt" speech, I use these parties only as an obvious example.)
This called the spoiler effect, and a runoff vote would prevent it. Right now more choices in the vote results in chaos and the candidate most people DON'T want ending up in office. With a runoff vote, there is no negative with more choice.
We saw this in action at the last Oakland Mayor's election. Now, if we can just set aside the qualities of Jean Quan (the mayor elected), it was interesting to see that the person who got the most first-place votes actually did not win. He was the "establishment" candidate, and both political parties were pretty pissed that the election had turned out unexpectedly.[1]
People may say that her election is a mark against IRV or RCV; but that's not the point! There will always be cases where someone incompetent gets elected. But the interesting thing in her case was that the groups who control the elections behind the scenes (PSUs, lobbyists, parties) were completely thrown off. Her election showed that it is possible for someone who is not beholden to the existing power structures to have a shot at election.
I believe runoff elections would though. Currently if one party runs multiple candidates something like this happens:
Democrat 1 receives 33% of the vote. Democrat 2 receives 33% of the vote. Republican 1 receives 34% of the vote.
Democrats had two strong candidates with some differing views, and decided to let both candidates run so the people would have more of a choice. The result is that 66% prefer a Democrat but a Republican ends up in office.
(Spare me the "their both corrupt" speech, I use these parties only as an obvious example.)
This called the spoiler effect, and a runoff vote would prevent it. Right now more choices in the vote results in chaos and the candidate most people DON'T want ending up in office. With a runoff vote, there is no negative with more choice.