This is basically how the caucus system worked and why Obama won in 2008.
Precinct organizers estimate the past 5-10 turn outs and say we need to get to “X” to win. That number may be 50, 70, 150 or whatever depending on the precinct.
When Obama won in 2008 the Clinton campaign used that formula. They would say we need 75 to win here. The organizers would show up with 75 and assumed they’d win. Obama’s team stacked the deck and would show up with 100-120 supporters. They vastly overrecruited knowing how the game was played.
Even in situations where it was deadlocked or a close tie and a majority was needed the Obama people basically sat down on their hands and said “We’re not going anywhere until we win.”
HRC and J.E. Bush can exploit the money part of it, but Iowa is all about bodies actually showing up. Trump, same thing. Iowa is all about turnout, turnout, turnout neighborhood by neighborhood, county by county etc. The big campaigns can oversell/oversubscribe numbers in the large media counties/metros but not the entire state.
Like I said, it’s a very convoluted process and never truly explained in depth by the media. That’s why the “winner” in Iowa frequently turns out to win nothing at all.