President Walter Mondale would tell you how important the size and enthusaiasm of rallies is. At the end of his campaign, he filled all of the Baltimore Inner Harbor, all of Boston Common, and all of lower Manhattan with wildly enthusiastic supporters, with numbers that dwarf any rally Trump has ever had. Observers were so amazed that they wondered whether the polls, all of which predicted a Reagan landslide, were wrong.
The polls were right.