Yes, usually you have to vote against some of your own interests because no candidate lines up perfectly with your interests. When people talk about voters vot

Yes, usually you have to vote against some of your own interests because no candidate lines up perfectly with your interests. When people talk about voters voting against their own interests I don't think they usually mean voters who know what each candidate's policies would do for their issues and vote for the candidate who will give them the best overall outcome given that all of the candidates would go against some of their interests. I think they are usually talking about the voters who don't actually know what a candidate's policies would do for their issues because they have been bombarded with misleading or outright lying ads from other candidates or from PACs or other organizations. For example in a US Senate race here a couple of years ago I saw a lot of ads from the non-incumbent all focusing on problems of the largest city in the state. The thing is none of these problems had anything to do with the incumbent Senator, nor were they problems that the challenger would be able to do anything about if they won. If the challenger wanted to actually address those problems she should have been running for mayor or city council. I've met several people who voted for that challenger because they wanted those city issues addressed. They knew she should be bad for other issues they cared about. So they thought they were compromising by giving up those other issues to get a better result on the city issues they cared about. But since the challenger would not have been able to do anything about those issues but would be able to do harm for the issues they cared about they ended up voting for a candidate that was not better than the incumbent on any issue they cared about and was worse on several.