The spores that cause late blight need living plant tissue to remain viable so the primary means of spread is in plant tissue such as the infected tomatoes that were sold this spring. The spores can remain viable on potato tubers all winter but those potatoes will also rot in storage.

Here is a link that might be useful: About Late Blight

I've read about the spores needing living plant tissue to survive, but I'm still confused as to whether my winter cover crop constitutes that living tissue, and if it will overwinter any late blight spores that might have been in the soil. Should I rip out the newly sprouted cover crop where my infected tomatoes were?

(Caroline, I hope I'm not hijacking - I just thought my question - and any answer(s) - might be helpful to you and others.)

Dee

digger asked "I'm still confused as to whether my winter cover crop constitutes that living tissue, "

No. The cover crop won't get tomato blight.

Unless that cover crop is also in the Nightshade family of plants.

I've put in hairy vetch. So I guess I'm safe - the late blight spores won't overwinter on the vetch, and I should be okay in the spring?

Thanks,
Dee

So why does my garden give my tomatoes blight worse and worse every year? I remove and compost pretty much everything and rotate the tomatoes between 7 different raised beds. I thought it lived in the soil. In fact, since it starts at the bottom of the plant, I assumed it was from soil being splashed up by rain. I mulch the tomatoes almost immediately after planting but I still get blight that crawls up from the bottom.

Well I can answer that one. The blight you're talking about is either Early blight or another tomato disease (there are many!). This discussion was specifically about late blight, which apparently does not live in the soil. Mine started nearly at the tops of my plants too.
The link that Kimmsr gave above had more info on tomato diseases, etc.

I guess mine does start in early summer, slowly at first but not late in the year. Just a few yellow leaves starting about the time the first tomatoes are ready...

toxcrusadr, what is your soil like? Have you had that soil tested? Have you looked into your soil with those simple soil tests I have outlined here many times?
While many people dismiss what I write here as malarky there are many more that have actually done what I have told them and they do not have problems like this. That you rotate and still have problems with plant diseases does indicate a serious soil problem that needs to be corrected.