It's possible that a dry root ball is to blame. Was this rhododendron planted fairly recently? If so, digging it up and soaking the root ball may be all what's needed to save at least some of the plant.

Another possibility is so-called stem dieback. This is caused by a fungal infection from phytophthora cactorum. Hot weather and less than perfect drainage are contributing factors in this disease. I'm not aware of any recommended fungicide for this. The best you can do is trim back to live, green wood, rake up and dispose of any fallen leaves and hope for the best. Rhodyman's website may have some more detailed information.

Another possibility I forgot in my first post is boytryosphaeria canker, another fungal disease. This is probably more likely in a drought stressed rhododendron in the landscape than phytophthora. Advice remains the same. Check the rootball, dig up and soak if it is dry. Prune back to green wood. Pick up and dispose of fallen leave.

There are some fungicides available to home gardeners that may help, but they tend to be pretty nasty and expensive. There are one or two "green" fungicides on the market, but I have had no direct experience with them.

I planted the rhododendron approx. 2 years ago, maybe 3.
Would it be too late to attempt the root soaking now?
I will definitely check out Rhodyman's website and weigh out the fungicides.
I just took this last photo a couple days ago.
You can see that it is still going downhill.
Thanks for the input!

It actually looks better in the more recent photograph. Leaves appear healthy and green even though there's a sizable patch of bare stems. What happens if you scrape away the bark on these stems? Can you see green cambium tissue anywhere? If you can, try trimming them back to that point. If the stems are clearly dead all the way to the base, cut them back to the bootom.

It does not seem terribly likely that a dry rootball would be the problem after 2-3 years, but possible if this has been a particularly dry summer. The leaves in the second photo do not suggest dryness at the root, either.

At this point, I'm not very confident in the fungal infection diagnosis, either. Could the patch of dead stems be the result of winter sun and wind exposure?

The die-back fungal infection and the brown leaf tips suggest a drought period in the past. The nice new green leaves indicate it is on its way to recovery. It may need watering in any future drought to prevent this happening again. Remove any diseased material such as dead leaves and dead stems. As aka mentioned, if the thin cambium layer immediately under the bark is not green, the branch is dead. Remove it and destroy it in the garbage or a fire. Do not compost it.

The die-back fungal infection and the brown leaf tips suggest a drought period in the past. The nice new green leaves indicate it is on its way to recovery. It may need watering in any future drought to prevent this happening again. Remove any diseased material such as dead leaves and dead stems. As aka mentioned, if the thin cambium layer immediately under the bark is not green, the branch is dead. Remove it and destroy it in the garbage or a fire. Do not compost it.