I find that following a few rules helps to keep my heterodox views from hurting my karma too much.

1) Keep them to myself most of the time. Pick my spots, in other words, and don't just toss off quick replies every time I disagree (who's got that kind of time anyway).

2) Don't make a factual claim without a link to back it up, even (maybe especially) if it's something everyone knows. There seems to be enough respect for the process of researching something and backing up your claims here, that people are less likely to downvote a fact they don't like to hear if you make the effort. (This is one thing that distinguishes HN from Reddit.)

3) Make the case dryly and impersonally. People are less likely to be triggered by disagreement if they don't feel like you're laughing at them or calling them stupid.

4) Include a "to be fair" balancing point if you can do so truthfully. For instance, if you're criticizing the Democrats, point out where the Republicans are also wrong on something.

Of course, none of this would be necessary to keep my karma positive if I were left-leaning, but that's okay. Communities should be allowed to lean whichever way they want, and there's nothing wrong with dissenters having to work harder to fit in.

This is exactly how I try to operate, and amazingly, it doesn't just work on hacker news, it works in real life!

I would add that oblique approaches work better.

You can sort of assume that everyone on here has (a) played this game before and (b) already seen the day's talking points on the rest of social media. Re-litigating that here is just a waste of time. Your (2) is absolutely critical here; the bystanders will upvote posts that have links to good sources that tell them things they didn't already know. Which is good! That's what the site is for!

Also remember: you can't convert the person you're arguing with. But it's the (invisible) audience who are handing out the scores.

Those are great points. As well as backing up facts with references, I would add, don't state an opinion without facts and reasoning to back it up.

And I agree that without doing these things, some opinions are more likely to draw down-votes than others. TBH I indeed probably am more likely to down-vote a badly made point if it's one with which I disagree. But really, everyone should be doing these things, regardless of karma concerns.

The delay timer option for submitting posts on HN's user configuration page is also helpful for that. Sometimes I will find myself making a post but then realize after a couple of minutes that it's not really worthwhile and then delete it before it ever becomes visible to other users.