Don't really see anyone on either side challenging him tbh. Oprah?
His approval rating is already 7 percentage points higher than Obama's was at this time during his tenure. I'm sure people like Jill Stein and maybe even Bernie Sanders may try to cash in one more time, but it's not going to matter.
I don't see the Democratic Party recovering after all is said and done with the multiple investigations and their recent bankruptcy. The Dems have been soiled with Radical Socialism and those kinds of stains are hard to wash out. The Information Age has not been kind to the Democrats either now that we have a clear picture on the history of their party. People like Dinesh D'Souza and Ben Shapiro are the real patriots enduring endless strife to deliver the uncomfortable truths.