Under first-past-the-post systems, as long as there are other people who support the greater evil, and evil's willing to use its power to increase its influence (whether that's removing anti-bias laws that restrict the press, raising limits on campaign donations, or more directly, things like gerrymandering), you'll get the shift towards evil from voting for the lesser evil, as the lesser evil will chase after the voters who vote for evil.

However, plenty of people notice that, and post memes like this one that encourage voting for a third party with no hope of winning or not voting at all, which only serves to accelerate the effect, as the lesser evil has to attract an even greater share of the evil demographic's vote to have any hope of winning. People say that voting third-party demonstrates to the lesser evil that it's worth courting non-evil voters, but that can't have any effect until the next election, and in the meantime, you're stuck with maximum evil for a whole term, and the hurdles to overcome grow larger.

The best hope is to start campaigning for a third party or non-evil candidate for the lesser evil party immediately after an election instead of leaving it until right before an election, as that hopefully gives enough time for support to grow enough that the lesser evil party will see non-evil as a meaningful demographic that's worth aligning with. It's not guaranteed to work, but if it doesn't, either evil is genuinely a majority and the democratic thing is to be evil, or the system isn't a democracy, and there's no way to remove evil by voting, so alternatives need to be considered.

No, you should vote for a different lesser evil that they prefer even though it will be even less effective

Their only solution is wait until enough people become leftists to have a successful revolution. They'll say it with a straight face like it's a realistic near-term plan.

Are you suggesting that a feeling of moral superiority while things get worse isn't a better solution?????