Washington — One week after Democratic insurgent victories in New York , the focus is now moving to Colorado, where challenges in a trio of races are threatening candidates backed by the party establishment — Senators Michael Bennet and John Hickenlooper and Rep. Diana DeGette. Bennet, who's represented Colorado in the upper chamber since 2009, had long been expected to sail to the nomination after he announced a bid for the governor's mansion last year. But state Attorney General Phil Weiser