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Sanders also would not rule out the idea of contesting the election results. The Vermont senator, who has introduced legislation to make election day a federal holiday in order to expand voter participation, also began to question whether some of the tactics reportedly used during the caucuses were "democratic."
"We want to look at some of the numbers," he told reporters in New Hampshire. "As I understand it, there were some precincts where actually delegates were won with a flip of a coin actually. ... Not the best way to do democracy."
Reports and videos emerged overnight showing some caucus rooms decided by coin tosses. Sanders noted that he and some members of his staff were traveling through the night, but that they were going to continue to look at the numbers alongside their local Iowa staff.
Speaking to an overflow crowd at a theater in town near his home state of Vermont, the senator said he was extraordinarily proud of the race his campaign ran in Iowa and sounded satisfied with the results.
"Last night in Iowa, we took on the most powerful political organization in this country," he told his supporters. "Last night, we came back from a 50-point deficit in the polls, and last night we began the political revolution not just in Iowa, not just in New Hampshire but all over this country."
Hillary Clinton meanwhile declared outright victory while also campaigning in New Hampshire.
"I am so thrilled that I am coming to New Hampshire after winning Iowa. I've won and I lost there, and it's a lot better to win," Clinton said.