At the offices of Mitt Romney, who has built a ground organization aimed at matching the intensity of his television advertising barrage, aides are methodically analyzing data on each voter to create the perfect pitch: those worried about illegal immigration are invited to join a conference call with a border sheriff in Arizona.
At Rick Santorum's offices, two of his college-age children, urgently aware that their father's presidential ambitions could end here, are offering potential voters a homespun message of family values. "What can I tell you about my father?" their calls begin.
And at the Michele Bachmann operation, lofty aspirations are rapidly fading into a dispiriting reality: the bells that campaign workers are supposed to sound with every new voter rarely chime.
Far from the spotlight of their candidates' events, hundreds of staff members and volunteers are scrambling for an edge in a fierce final effort to tilt the outcome of a contest that has been shifting almost by the day.
Beyond the speeches and television commercials, this unglamorous ground war is unfolding with hidden intensity inside forlorn office parks, under pale fluorescent lights and amid grease-stained pizza boxes.
Yet in the closing hours, it is the tedious and time-consuming work of identifying voters and persuading them to show up at Tuesday night's caucuses, the first contest of the 2012 election, that could make the difference among Republicans who cannot seem to make up their minds.
As the days dwindle and the pressure rises, these behind-the-scenes deliberations and strategies offer telling insights about the state of the race, the strength of the campaigns and the personality of the candidates.
There is the quirky insularity of Ron Paul supporters, skittish in their bow ties and fleece jackets, content to keep opponents guessing as to whether they should be feared or ignored.
There is the triple-checked orderliness of the Romney campaign and the good humored chaos of the Gingrich operation. Though the onetime front-runner Rick Perry flaunts his deep pockets on the airwaves here, perhaps a more revealing assessment of his status can be found written on the walls at Gingrich headquarters, where Mr. Perry is the only one of six candidates reduced to a humbling shorthand: "Other."
And while the lights were off and the doors locked at the Bachmann headquarters the other night, there was a renewed sense of possibility at Mr. Santorum's office, up and running past midnight, where staff members have been dismissing the once pervasive questions about electability with increasing confidence.
"I don't know if you saw the poll that came out tonight?" one Santorum worker told a voter.
In a big, sparsely populated state, where knocking on doors is impractical, the crucial tool of campaigning is the trusty telephone. Every evening, campaigns are following the time-tested method of packing volunteers into their headquarters to place as many phone calls as possible.
The energy level in these rooms, however, varies considerably.
Inside Mrs. Bachmann's office near Des Moines, a political adviser laid out an ambitious plan for the final week. The campaign would tap an army of supporters to call 25,000 undecided Iowa voters who could make the difference between a respectable or an embarrassing finish for her candidacy.
On this night, it was off to a rocky start.
There were only three volunteers working the phones. One struggled with her computer, then took an hourlong dinner break. Another dialed a Bachmann donor, who promptly told her he was no longer interested in the candidate.
"He's been watching her the entire time, but just thinks that Gingrich will make a better president," she explained to her fellow volunteers. "I am not going to argue with people."
During nearly an hour of technological troubles and busy signals, the reception bells sounded for every new supporter rang just once.
