The moment we Leave, if we do, Leavers will completely cease voting on the basis of what they think about the EU. Nobody casts their vote as a thankyou. Look what happened to Churchill in 1945. So can we get away from this idea that delivering Brexit will earn Johnson some kind of thumping majority. The country will revert to voting on the basis of other things and if anyone gains it will be the Lib Dem’s, hoovering up angry Remainers from both the other parties.
A polling card is not a thankyou note.