Approval voting seems to me to be worse on all counts that the previous commenter was levying against ranked-choice. To your point, the spoiler effect seems like it would be much worse with approval than with a ranked ballot, since highly partisan voters would have little reason to approve of any candidate other than the single candidate they want in office. Approving of anyone else lessens their candidate's chance of winning.
A ranked choice ballot at least requires you to assign a unique value to every candidate on the ballot: you can honestly rank your second choice without being concerned that doing so undermines your first.
>A ranked choice ballot at least requires you to assign a unique value to every candidate on the ballot: you can honestly rank your second choice without being concerned that doing so undermines your first.
That's highly implementation dependent. Where I live we have ranked-choice ballots for local primary elections, while the local general elections are FPTP. State and Federal elections are all FPTP for primary and general elections.
While I am free to rank up to five candidates when filling out my ballot, I am not required to use all five choices.
I can just ignore all that if I choose and just rank one candidate first and leave the rest of the ballot blank. Or I can rank multiple candidates, but I'm not required to "assign a unique value to every candidate on the ballot."
In fact, if there are more than five candidates for a particular office, I can only rank five of them.
All that said, I'm absolutely in favor of RCV and wish we had it for all elections, not just local primary elections.