Sometimes supporters of top-two open primary systems say that their system eliminates “spoiling”, i.e., the so-called tendency of minor party candidates in a race to alter the identity of the winner. But, that argument is faulty. This is clearly illustrated in the First Assembly District results in California’s June 5 primary.
Two Republicans ran: Brian Dahle received 31,687 votes, and Rick Bosetti received 25,820 votes. They will be the only candidates in November. They are both firm opponents of any tax increases. In addition, one Democrat, Robert Meacher, ran. He received 24,081 votes, not enough to qualify for the November ballot. Also, Green Party member David Edwards ran, and received 5,225 votes; and Libertarian Charley Hooper ran and received 4,839 votes. Here is a newspaper story, in which the Democrat, Robert Meacher, says that if the two minor party candidates had not been in the race, he would have received enough votes to qualify for the November ballot. See the fifth paragraph in the story. Meacher is probably correct.
Assembly District One consists of the northeast corner of California. If California still used a normal system in which party members nominate candidates for the November election, voters in this district in November would be able to vote for any one of four parties, for Assembly. But, in reality, voters will be restricted to choosing between two Republicans, both of whom are very similar on the issues.
If top-two supporters are sincere that they wish to eliminate “spoiling”, it would be more rational for them to support Instant Runoff Voting or Approval Voting.