Funny, I always thought it was cirrhosis — a number of sources say as much — but it seems like the cirrhosis just made the fall more deadly, if it was related at all.
So you’re right, the fall itself is definitely butterflied. Still, he was definitely not in good health and had been suffering from serious liver problems for years. If Daniel makes it to 1852, he’ll be at death’s door, and the stress of the office won’t help. Given his personality, I have no doubt he’d run for re-election, but he probably wouldn’t see his term through if he won.
I’m still not sure how much he’ll be able to get done from 50-52. He’ll try his damndest and might even do a decent job, but his sharp tongue definitely didn’t help him reach across the aisle. I have a feeling he’d push for major reforms, but without the mandate that comes with actually winning an election, I’m not sure much would come to fruition. He would rile up his opposition like crazy, though—whatever Webster’s fate after becoming President, we might even be seeing an earlier secession crisis.