By early November, it's probably too late, yes. Our Lawns and Microclover resource (and the PDF planting guide it links to) says that:
"The preferred time to seed a turf-type tall fescue/microclover lawn is in the late summer to early fall. While successful seeding may be obtained in late fall or during the spring, the risk for a poor stand increases substantially due to weather related problems such as heat and drought, and from competition from both broadleaf weeds and annual grasses such as crabgrass."

Right now, the daylength is so short that we doubt much will germinate or establish well before colder weather and shorter days shut down growth, even with a few degrees of temperature buffering from a frost blanket. (Avoid plastic, which can trap too much moisture or humidity, leading to fungal damage. A woven fabric, like row cover, is better.) If you try sowing now, some seed might wait to germinate until spring (if it survives the winter), but wildlife might eat some of the seed in the meantime, so that's not an ideal alternative. Any clover that does germinate will lose its above-ground growth once we start to experience freezing temperatures.

Miri