So is this a serious thread or just an excuse to trash talk a politician you don't like?
Because if it's a serious thread, I expect that when 2020 rolls around you'll see an internal GOP squabble as the big headline. The Romney/Bush/Uncle Pennybags faction of the GOP isn't likely to die off quietly or migrate over to the DNC willingly. So expect a candidate to challenge Trump in the primary. And if Trump doesn't follow through on his promises about jobs, healthcare, and immigration, he could actually lose. It's easy to make big promises on the trail, but if you can't deliver folks will turn on your fast.
From the DNC side of the aisle? I'd expect Cory Booker. Elizabeth Warren may run, but she won't be seriously trying to win. She'd just be looking to become a major player in the party.