All that said, there is a difference between Trump and the Cain, Gingrich, Perry, and Giuliani boomlets of years past. One can wonder about how well the polls represent the likely GOP electorate, but Trump has across the board support from virtually every sub-group that comprises Republican primary voters. Trump also continues to attract immense amounts of media coverage and is generating huge TV ratings. Furthermore, he is driving the discussion in the race—shaping what his opponents say and do on a daily basis.  None of this was the case with previous shooting stars.

Does anyone think that immigration would have this high a profile in the Republican primary if Trump was not running? Does anyone think that is a good thing for Republican general election prospects?

The evidence suggests that Trump will not just fade away. He will need to be engaged with the blocking and tackling of election campaigns, and how that is done will have an influence on the nomination fight and, ultimately, the general election.

Put another way, even if Trump is a summer fling, the nature of those flings and how they end can matter.