Redistricting plus California’s new open primary where the Top Two regardless of party advance to the general election, has pitted two Democratic members of the House and former allies, Howard Berman and Brad Sherman, against each other in an increasingly nasty campaign.
Open primaries were designed to give independents more of a voice in the primaries. However, open primaries hurt third parties because it greatly decreases their chances of having a candidate in the general election. It also means the general election can be between members of the same party. This can be divisive and bad for party unity, of which the Berman Sherman fight is the most visible and is getting national attention.
I’d say the jury is still out on whether open primaries help more than they hurt.