Thanks for your question about your clematis. In general, these are hardy, perennial plants that need only sunlight, cool and moist but not wet roots, and something to support them. I'm unable to see from your pictures what type of soil they're in, or whether there's a drainage problem. I also can't see from the leaves whether there might have been some sort of fungus that grew on them. (Monitoring plants for signs of disease is essential to curing the problem before the leaves, etc., are dead.) Since your plant appears to be under a patio cover, and untouched by the rain, the growth of airborne fungi is less of a risk. However, the leaves look incredibly dry, so I'm wondering if it received inadequate moisture. You might also have added too much lime, changing the pH too much for the plant's liking. They prefer slightly acidic soils (6.0 to 7.0--neutral). It's always dangerous to add lime to soil if you (1) haven't measured the pH and (2) don't know what pH is preferred by the plants in it. You can buy inexpensive pH test kits at most garden stores. Do you see any new growth at all? I can vaguely see some green, but can't tell if it's on this plant or not. To see if it is dead, you can cut off a vine a foot or so from the ground and see if it is still moist, and white to light tan inside. If it is dark brown or black, it is unlikely to re-generate. Nothing will restore these leaves to health, but assessing whether it has just lacked enough water and correcting that may spur it back to health. Hope this is helpful. Good luck!

Thanks for your help! I cut a couple vines like you said, and they are light tan/greenish on the inside, and the pH is now at 6.25, so I hope those are good signs. It is under a patio cover, though I've been watering it since spring. I'm attaching a picture of the whole plant.

The green you saw was this plant--where it started to grow and blossom in the spring before it wilted, those leaves are still there and soft but very wilted. And the blossoms never opened.

I hope it really is just a matter of needing to water more. If there's anything else I should check on it, though, I appreciate your guidance.

Thank you,
Ali 

Thank you for the added information. I see from the new picture that there are yellow spots on the lawn next to the clematis' roots. Have you been trying to kill any weeds in the lawn by applying something like Roundup? Herbicides can migrate through the soil, and get taken up by adjacent plants. And is there a hot tub or other reservoir under the tarp to the right of the plant's roots? A leaking hot tub can kill roots with too much chlorine. Just looking at all options....

Good ideas, but no. The grass got a little long and we just mowed it, so that's where the yellow spots came from. It's just a normal concrete patio behind. I just had the tarp out because I was painting a craft project. 

I did use Weed n Feed on the grass once in the spring, though. Could that have done it?

Hmmmm. Did this dieback start after you used the paint, or before? Was it an aerosol paint?

We don't recommend Weed and Feed. And over-application (more than recommended by label) can kill surrounding plants. Kill weeds selectively--preferably by digging out. Most lawns don't need extra fertilizer, and organic--compared to chemical--is preferred.

Okay, so if it was the Weed n Feed, is there anything I can do to help it recover?

The paint was months after the wilt. 

I'm going to need to research the Weed and Feed once I'm back to my computer tomorrow, and let you know. Perhaps there's something I'm overlooking. A mystery!

I have tried to find an answer to the Weed and Feed question, and I haven't found anything too helpful.  However, the weed killer in Weed and Feed (2-4-D) kills any broadleaf plant it touches (and clematis qualifies as such).

The label says:  "This is for grass not flowers, shrubs, fruit and vegetable plants. If accidental contact with other plants is made rinse off immediately to mitigate damage."

This article (not coming from science-based research programs, such as universities) indicates that either drift (which is a caution on the Weed and Feed label) or operator error (ditto) may allow it to impact adjacent plants--which your clematis certainly qualifies as!  (Here's a link to a Michigan Extension article about the hazards of using 2 4 D close to grape vines, structurally not too different from clematis.)

You just have to decide whether you want to cut it down and plant something else, or wait to see if it revives.  We've explored all of the potential causes of its decline that I can find in the literature, and I just can't offer more assistance.

Good luck, and limit the chemicals!

Okay, we'll watch and see for a little while. Thanks for your help!

Fingers crossed!