I now have to answer my own question, having withdrawn my nomination.
I explained in my nomination that I would stand aside if there were a sufficient number of strong candidates. As there were 5 others, and I couldn't see a combination of winners that would be unsuccessful*, I followed through on my word, and withdrew my nomination.
I want it to be absolutely clear that this is not in any way a vote of no confidence in the site, SEI or the other nominees. I expect to be remain an active member of the site (perhaps a little more focussed on researching answers to questions, but still patrolling around sticking my nose in where it isn't needed.)
It should also not be taken that being a mod isn't rewarding. It has been a great experience, and I am proud of what the team has done.
My reasons for withdrawing consist of several minor issues that add up:
For the last few years, I have been deliberating allocating more of my time to creative and interesting projects. Most of them are measured in weeks. When I agreed to be a mod, it was for a short-term, until the elections; it took much longer than I expected. I've already drastically exceeded how long I thought my attention span would last on this site. While I am not at all bored of the site, I don't want to commit to something I can't deliver; I don't want to run for mod, and then start drifting away after only a few months.
I want to see the site constantly improving. However, I think I am out of new ideas. I have tried out a number of different ideas as mod. Some succeeded. Some failed. Some were impossible. Some I was persuaded were silly.
When I try to think of what I want to do next, it is limited to small ideas that don't need mod powers. (I want to write some reports when our data is published. I want to test some ideas on writing for different reading ages, to see whether it is better to write as though you are talking to an undergraduate, high school student or primary school student.)
So, I want to step aside and let people with ideas lead.
We are in a different stage. We are graduated. We have a community. I'm aware that different sorts of leaders are required at different stages, so it makes sense to let some new talent in.
I am almost at 20K rep. At that point, you become a "trusted user". Mods have more powers than trusted users, but not by much. I can continue to do almost everything I do now, but without taking any of the flak! If you want me to be mod, go find one of my old answers that you like an upvote it, until I get to 20K. (If you see any you don't like, of course you should downvote them. It is the only way I will learn.)
In an ideal world, the regular users would take on most of the roles the moderators currently do: welcoming new users, closing questions, editing salvageable ones, asking for references, discovering duplicates, handling flags and suggested edits. None of that requires a blue diamond. The trend is definitely heading that way - I am very appreciative when I find people have beaten me to it. I hope to lead by example there.
So, in summary: Still happy. Still hanging around, until I get distracted, and I am not yet. Still expect to see my comments on your questions.
* With the current candidate list, at least one existing mod must be re-elected. I suspect that if only one mod was re-elected, there would be a longer settling-in period for the new mods. It took me weeks of watching the others before I was comfortable to make many decisions myself, but I am sure it would be fine in the long term.