Wouldn’t it be great if you didn’t have to vote for the least horrible candidate? If you could vote for who you wanted without feeling like you’re throwing your vote away?
If we had ranked choice voting, we’d have better legislators in office to start with. And if they used it in the speaker votes this could be resolved already.
There are lots of options. Someone else mentioned a default option (something like “whoever in my party has the most votes”), or simply making an exhausted vote just continue as a vote for their final choice (which prevents the plurality win mentioned above). And you wouldn’t need 400 runoffs, they could just nominate valid options beforehand and require ranking everyone. These are choices that would need to be defined in setting up RCV.
And even if the rule was “exhaustion = voting present”, Republicans would almost certainly vote for the Republican they dislike rather than risking a plurality Democratic speaker. They’re voting for random other people now to force a change of choice, but if it was resolving one way or another all at once, their choices would be different.