That makes sense if you think in terms of parties. But if you're interested in policies instead, I think it might be wrong.

For example, if you want them to do something about climate change you might vote for the Green party instead of Democrat. They won't win but your "stolen" vote might cause the Democrat party to lose. They don't want to lose so they might adopt policies from the Green party to attract you and all Green voters. That would be as good an outcome as multiple parties.