I don't think Obama will win NY, but even a strong second would be a boost:

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Obama Giving Clinton a Race in Her Backyard

By SAM ROBERTS

Published: January 12, 2008

www.nytimes.com/2008/01/12/us/politics/12york.html

With Senator Barack Obama vowing to challenge Senator Hillary Rodham Clinton on her home turf, the Democratic presidential primary in New York on Feb. 5 is shaping up as the state’s most competitive since 1992, when Bill Clinton took up a rival’s mantra of change to all but cinch the nomination.

Mrs. Clinton was re-elected a little more than a year ago by better than two to one. Before the Iowa caucuses, she had so dominated opinion polls and endorsements by elected officials and powerful unions that many considered her home state impregnable to political interlopers.

But if Mr. Obama wins the South Carolina primary in two weeks, he could develop enough grass-roots support among young people, liberals and black voters in New York to pose a serious threat to her claim to the state’s rich delegate lode, allies of both candidates say.