The Times also mentioned a few others who were positioning themselves for a run should Trump not be up to running for a second term, and why not? Trump's form so far has been less than brilliant and a bad showing in the mid-terms might start  mutiny in the ranks. 
This also might explain the high dudgeon expressed by some Republicans when a Trump like character was cast in the role of Julius Caesar earlier in the summer. Their protest over the murder of Caesar was well over the top demonstrating either total ignorance of the plot or perhaps the play pricked their consciences. Et tu, Pence?