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Since the start of the season, the hierarchy of men’s college basketball has been constantly changing.
This week, when Gonzaga took over the top spot in The Associated Press Top 25 poll from Kansas, the Bulldogs became the sixth team this season to be No. 1. Any of those No. 1s, a group that also includes Michigan State, Kentucky, Louisville and Duke, could win the N.C.A.A. tournament, and all will certainly be key teams in the race for a national title.
Still, one by one, the big-name programs have faltered early this season, sometimes in surprising fashion.