Which campanula are you asking about?

If its a ground hugging one, when you dig it up you'll find it isn't lots of little plants, it's one big one with parts of it not showing topgrowth. You can certainly split it into sections and replant, but not now - either in late September or next Spring.

Thanks Bamboo - with trying.

MG - have uploaded a pic of the blue one from last year - it did not re-flower.