135,000: The magic number that could decide Trump versus Cruz in Iowa

That hasn’t stopped some Republicans from forecasting an enormous uptick in voter participation. Kaufmann has asked GOP officials around the state to prepare for as many as 170,000 caucus-goers, though he says he expects 150,000 or slightly less. The latter figure is being floated by Governor Terry Branstad, who has told allies that he expects shocking levels of participation on Monday.

Those are high-end estimates, however. Officials from many of the campaigns predict the number will fall somewhere between 125,000 and 140,000. A few even think the figure could remain relatively static at 122,000, arguing that Ron Paul drew many first-time caucus-goers in 2012 who won’t be back this time.

“With all these candidates, all this turnout effort, it’s logical that we’ll have a record turnout. But it’s illogical to think we’ll double the record turnout or that it’s going to go to 170,000,” says Iowa representative Steve King, a Cruz supporter. “I think Cruz wins this in a close race, with a 135,000 turnout number as the over/under, and I think we go under that.”

The Cruz campaign has done extensive modeling on the caucuses and believes the turnout will ultimately fall between 133,000 and 137,000. Republicans familiar with Cruz’s analytics program say his team has modeled caucus electorates all the way up to 175,000 out of an abundance of caution, and feels confident that its man will prevail even if turnout reaches that high. The reason: Cruz will hold a lead of roughly 7,000 votes over Trump with a GOP electorate of 125,000, his allies say. Trump would need to win a huge plurality — if not a majority — of additional votes in order to offset Cruz’s lead.