Republicans face all kinds of obstacles of their own making if they are ever to return to power in California.

They also face a potent opponent in top two.

Indeed, top two now looks like a key piece of the one-party state Democrats are building. It will make it hard for the GOP or any smaller party, old or new, to challenge.

At heart, the problem is that top two shuts parties out of November elections (I refuse to repeat the state’s error of calling November elections general elections, since they really are run-offs; June elections are general elections). In more and more races, we’re likely to see Democrat on Democrat races.

That is not a side effect of top two. It’s the desired effect. The good government reformers behind top two thought they could elect more moderates by encouraging top two runoffs between candidates of the same party. The idea is that candidates would compete for voters of the other party, thus encouraging moderation.

Top two doesn’t actually work that way. It’s boosted the more liberal and more conservative candidates, who need bases to get through the first round of top two races that can have dozens of candidates.

And in the second round runoff, it turns out that moderates aren’t strengthened. Because when voters of one party don’t have a candidate, they often leave the ballot blank or don’t vote at all. A recent CalMatters analysis found this was true again in this year’s November races.

For Republicans, that means there are many races where they won’t have a candidate or the opportunity to drive a message or encourage voters to turn out. If the Greens or the new party California needs (such a party should be focused on young people and be managed largely on the Internet, but that’s another story) are going to push to replace Republicans as the main opposition, top two will stand in their way too.

That’s why the Republicans and other parties should focus their energies on overturning the top two system as the first step to reverse one-party rule in California. They’ll be doing themselves a favor. They also will be serving democracy.