There has been more than one poll showing Trump with larger leads among registered vs. likely voters.
This is where GOTV operations are crucial. The vote of an unmotivated / disinterested voter counts just as much as an enthusiastic voter if they actually show up to the polls and vote...(or in the case of vote harvesting, someone showing up with a prefilled ballot going door to door getting them to sign off and then dropping it in the drop box).