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The campaign had made more than 1.4 million phone calls to voters and 6,000 volunteers canvassing the state in the last few days.
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In the end, though, key voting blocs were there for Clinton in New Hampshire — or weren't there for Obama, depending on how the campaigns frame it. According to exit polling conducted by The Associated Press and the networks, far more women voted than men; Clinton won 45 percent of them compared to 36 for Obama.
Also according to exit polls, only half as many New Hampshire voters under 30 turned out as in Iowa, depriving Obama of crucial support.
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The campaign organized down to the precinct level. They built lists of endorsers and volunteers. They spent more than $5 million on 5,000 television ads in New Hampshire media markets.
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----- I included those paragraphs which highlighted her work and on-the-ground organizational ability, but there's much more at link and a really interesting read:
http://talkingpointsmemo.com/news/2008/01/clinton_squeaks_out_win_over_o.php