As we await the Idaho primary results, here's an interesting fact: You can register to vote at the polls if you bring proof of ID to the polling station. This could play into the general Trump campaign theme that he can win because he has a lot of crossover vote.
However, this could also prove to be a double-edged sword as those same liberals crossing over will end up voting for a Democrat in the general election 99% of the time. If Trump can't convince them to stay, then there is no way he beats Hillary... which is what practically every other Republican has been saying this whole time. In terms of campaign strategy, this is almost as risky as bragging about the size of your manhood on national television.