Looking at the crosstabs:
http://i2.cdn.turner.com/cnn/2014/images/02/04/rel3a.pdfyou can see that, again, even in his weakened state, Christie still has more crossover support than the other Republicans. He gets 10% of Democrats to back him in the GE matchup with Clinton, higher than any of the other Republican candidates can manage. And his deficit with Clinton among Independents is "only" 13 points, which is a narrower loss than the other GOP candidates. It's just that he suffers more defections to Clinton among Republicans than the other candidates do, so his overall numbers aren't great.
One other notable thing on this is that Christie is notably stronger in the Northeast, compared to the other GOP candidates:
Bush vs. Clinton:
Northeast: Clinton +34
Midwest: Clinton +14
South: Clinton +12
West: Clinton +24
Christie vs. Clinton:
Northeast: Clinton +13
Midwest: Clinton +28
South: Clinton +4
West: Clinton +22
Ryan vs. Clinton:
Northeast: Clinton +29
Midwest: Clinton +20
South: Clinton +7
West: Clinton +12