my guess is it is drowning. One thing I learned recently is the teacup effect of a freshly planted tree or bush. water will easily penetrate into the hole you dug and stay super soggy in that loose soil. I don't have a solution to saving it at this point, pure guess work would be to remove some leaves so the severely damaged root system has less to try to support.

Ken, Here's a pic before I staked it: This is it almost exactly a year ago from pretty close to the same camera angle but much closer up (you can tell how much the foliage has increased by the sheer # of leaves): There are two main leaders at this point, both suffering from the same top-heavy problem and leaning in the same direction. So I used two 6' plastic stakes about 2 feet away and twine+velcro straps to pull them upright and slightly separate them. How long do you think I should expect to leave it staked? I'd rather not do it for long if I can help it . . . just long enough for the branches to strengthen. It didn't have this problem last year but I'd say it has >3 times the foliage now. It's definitely a JM but I can't guarantee how true to bloodgood it will be. It grew up under a mature bloodgood at my dad's house, presumably from seed? Either way I'm expecting it to be large for a JM . . . its parent tree is probably 15' high with an 8-10" trunk, and is at least 15-20 years old. This one is in a spot where that size would be fine, so I'm not worried about its growth potential . . . I just don't want abnormally fast growth to keep it from being the beautiful tree it has the potential to be. Thanks again.

Check the roots, either it is not getting enough water, it has roted, bugs got it a rat dug it out, a dog peed on it. too much sun. wrong soil, to much fertilizer, not enough fertilizer at the right time. It has gone dormant. etc etc. I can't see your plant dig it out and start over, they are summer growers where I live and start to flower in Jan. many of them still flowering depending on the species. Mine as flowsered a set seed already. Glad to help if you give me more inforamtion. There are very sharp people on this forum, Species name will be of help, if purchased at home depot, or any of the like stors, or purchased recently, it may have been a sick plant when you got it. If planted in situ, the soil may be sick. It is a tiny little plant in a four inch pot, it just didn't have room to grow and not enough new mix for it to last a year. It's a crap shoot with the information that you provided.

Close up views can be helpful in determining what's wrong but, here, it's challenging to know how this view related to the whole. Please post a picture of the entire plant/planting. If that's not possible, my guesses are too little light, possibly too much water.