ANKENY, Iowa – At nearly 9 p.m. Saturday, Samy Amkieh was about to head back to his office after braving 20-degree temperatures to knock on doors for three hours in East Des Moines. But the 20-year-old field organizer knocked on one more door and was rewarded by convincing the resident to be a team leader for Bernie Sanders at a nearby caucus location. “When you think you can’t go any more – that house is too far away, it looks really icy down the street – just remember that every single person you’ve talked to, the odds are they haven’t been pulled in by us or by anyone,” he told a crowd of nearly 100 Sanders volunteers Sunday, aiming to rally them to head out into the cold yet again to knock doors for the Vermont senator. One week before the Iowa caucuses, Amkieh is one of hundreds of campaign staffers and volunteers fanning out across the state doing the behind-the-scenes work that can lead a candidate to victory.