Some of the explanation lies in the particulars of the campaigns arrayed against Romney. None of the other candidates have much money, and organizing Iowa is expensive. Rick Perry, who does have money for his campaign, got in the race late.
Michele Bachmann won the Iowa straw poll in August, but then ditched the campaign manager and consultants who were advising her to keep up a laser-like focus on Iowa. Rick Santorum has run the most Iowa-centric campaign, visiting all 99 counties himself and campaigning tirelessly in town after town, but he lacks the funding to build out a full-fledged professional operation.
Two of the race's buzziest candidates, Cain and Gingrich, have pursued media-driven national strategies, to the point that both have lost disenchanted staffers who concluded they were more interested in their book tours than winning the primary. (Gingrich, now getting his second wind in the campaign, appears to have buckled down since those unserious early days.)
Ron Paul, the eccentric Texas congressman, is generally acknowledged to have the best Iowa campaign organization, a fact that helps to explain how he's vaulted into contention in the state despite being ideologically outside the Republican Party mainstream.
But ironically, the biggest reason no candidate has risen to challenge Romney in Iowa may be Romney.
The fundamental dynamic of the absentee front-runner has created a sort of reverse arms race in Iowa. Without a well-funded candidate dumping resources into the state, the organizational bar has been lowered, and the rest of the candidates have set their sights lower as a result.
"Mitt Romney set the pace last time," said Rep. King, adding ruefully: "He has perhaps set the pace this time as well."
Joe Gaylord, the veteran national Republican strategist who began his career in Iowa in the 1970s, said recent caucus cycles have seemed to reward the last-minute surge over the elaborate long-term plan. But there's also a sort of game of chicken going on.
"Because no candidate has started a huge organizational effort in Iowa, the others have also found it worthwhile for their campaigns not to do it right now," he said.
And so despite the way he's downplayed the state -- taking fire for it from Iowa partisans -- Romney still has one of the best Iowa organizations of the 2012 campaign simply by keeping in occasional touch with his 2008 supporters.
"They haven't been playing the game in the normal way, with a big event to open the campaign office and lists of people lined up as county chairs," Selzer, the Iowa pollster, said of Romney's crew. "But they still have people in every county. They have precinct people lined up. They have not been showcasing how much work they've actually been doing in the state, but they are positioned for a surge if they think there's a chance they could win."