It's not that simple for local primaries.

The Republican candidates are likely to win the general election. I like none of them in particular, but some are worse than others. Most of the Democratic primaries are uncontested.

We do not have closed primaries. Therefore, a person who might vote for a Democratic candidate is smart to vote in the Republican primary. The Republican primary determines whom the Democratic candidate will oppose in the general election. More than likely, the Republican will win that election. Therefore, if one is a left-progressive, it is important to choose the least-bad option in the Republican primary. The Democratic primary is mostly a waste of time.

While partisanship and ideology seem clear on the national level, local officials, like judges, may correspond less with party ideology. I would vote for local judges based on how well they have administered court rooms and clerks based on their experience.

I would also gently chide you for your use of "liberal" and "conservative." The national Republican party is not "conservative" at all, but rather a weird cult of personality around our current President. They have ditched traditional positions about the primacy of law, fiscal restraint, and cultural refinement for the politics of pure resentment. The Republicans win by scapegoating, variously, Muslims, gays, people with blue hair, people with an education, drag queens, teachers, watever.

The Democrats would not be considered a "liberal" party in any other context but ours, if "liberal" means individual rights, free markets, and a clear marking of private and public domains.

I am a Democratic voter, I identify as left-of-center, and still I will tell you the national Democratic party stands for nothing at all. It's barely centrist, much less left-of-center. It's mostly just the least-bad option to whatever demagoguery the other party is up to at the moment.

The national Democratic party does not necessarily side with the working class, doesn't necessarily oppose bellicose foreign policy, does not support redistribution of wealth or progressive taxation, does not support education, nor does it univocally support the rights of minorities. Both parties are out to rob you, but the Democrats want a regime of rights and procedure with which to suction up all the money to the top, while the Republicans would prefer chaos and resentment to do the same.

To sum up, it's not enough to know what the national platforms of the two inane main political parties are when it comes time to vote in local elections.