Florence to Santa Margherita Ligure

The main problem is that the train to SM from Florence will be the train "to Cinque Terre" even if you are riding it past there. I had to change trains and rode it briefly on the way to Pietrasanta in September of 2024 and the train was packed full of people (presumably) all heading to CT. Getting on part way through the trip and I had to stand in the crowded doorway area for the few minutes I was on the train since my stop was well before La Spezia. I see a 10:28 train that changes in Pisa and continues all the way to SM but even if doesn't stop in La Spezia it will be packed people getting off there.

I can't speak to whether or not you will find it crowded but crowds in train stations tend to be temporary since people tend to be moving onto another train or out into the city. You could go early to (hopefully) avoid crowds and you could also look at the gap between trains and if it is more than a few minutes you could go outside and wait it out before heading back to meet your train.
On the Friday in September I'm looking at I see an 8:28 that goes past La Spezia and onto Chiavari where you transfer to SM. And then you'll have to schedule your trip back.

The ugly reality is anything on the coast north of Pisa is going to be caught up in the coastal summer crowds and the tourist crush of CT. If you really want to avoid these crowds you'll either need to look in other directions or other modes of travel. You could look into booking a tour with a company that provides transportation or just a dedicated NCC driver but neither of these will be cheap. I know there a few buses that do the coast but unfortunately I think La Spezia is a prime hub for changing and you're back at the same spot.

If you really want to go hopefully there is a coastal bus service that I don't know about. And the last thing I will say is that whatever way you go it will be 3+ hours to get there and, for me, that is generally beyond the limit I would set for a daytrip. The trip with someone driving is way more relaxing but 6+ hours of travel for one day is a lot.

Have a great trip whatever you decide,
=Tod

Ditto to what hiredman has said: you're going to go through the CT region from Florence any way you shake it: you'll change trains in either La Spezia or Pisa, maybe both, or Pisa + Chiavari, depending on which departure time/length of journey you prefer. Actually, the Florence + Pisa + Chiavari route would have you avoiding La Spezia but doesn't leave Florence until 13:28, and is 2 train changes versus 1 but, well, it's an option.

As you say you're traveling mid-day, I'm guessing that Santa Margherita Ligure is your final destination for an overnight (or longer) stay and not a day trip? It really is a bit too far for a RT in one day.

Thank you both! To clarify, this is not a day trip. We’ll be staying in Santa Margherita Ligure for a few days.