DES MOINES — The adage about the best way to win the state caucuses, credited to former U.S. Rep. Dave Nagle from Iowa, is to organize, organize, organize — and then get hot at the end.It would seem less than ideal, then, for any serious caucus candidate to organize, organize, organize — and then leave the state at the end.Yet that is precisely what three serious players in the tight Iowa race are doing.