California's primary for governor is undecided as candidates vie to be in the top two

[RockRaven]

30. It prevents run-offs by keeping the general election to two candidates instead of

one candidate from each party (which usually resulted in 4-8 candidates on the ballot), which could lead to the highest vote getter being below 50% -- which then would require a top 2 runoff.

That is pretty much the only advantage.

The system exists the way it does because it was instituted via Proposition 14 during the Governator's reign, designed by a Repug state legislator/Lt Gov. Along with the citizen redistricting commision, it was part of Repug efforts to bamboozle the naive public into structurally helping the Repugs win, via appeals to fairness and efficiency.