content: Ignoring any failures on this particular scheme, anything that encroaches upon the perceived ability of an elected official to be re-elected has a built in bias to refusal from those who can actually implement the change.  In short, if it the chances of getting elected go down then why do it.    The two major parties occupy essentially all offices of any level of power and can thereby ensure they have an effective 50% chance for their party to maintain control.  Widening the available choices, no matter how it's implemented, will reduce the chance of a major party candidate holding office than when there are only two perceived choices.