In 1980, Democratic pollster Peter Hart warned Gaylord Nelson, Wisconsin's champion vote-getter as governor and senator, that he was going to lose. Hart saw a Republican wave coming. Ronald Reagan would defeat President Jimmy Carter and carry other GOP candidates to victory as well.
The opposite of the wave effect in elections is the so-called Eisenhower jacket, a term coined by Democrats predicting that the immensely popular Ike wouldn't have the coat-tails to help other Republicans down the ballot.
With three months to go in the 2016 race, there is a presumption among most Democrats and more than a few Republicans that Hillary Clinton is headed to a decisive victory. Democrats are talking about a possible wave, while Republicans see a no-coattails election, particularly since Clinton herself remains unpopular.
Of course, the race could change. Trump could get his act together, or there could be a crisis or a Clinton contretemps.