According to a poll from the Associated Press, the race was called at only 21 percent reporting, at which point Clinton had already won 40 of the 85 proportionally allocated delegates up for grabs in Arizona, the most critical state of the night for Democrats. She also grabbed 60 percent of the thus reported votes.
The former secretary of state was widely expected to win the state, where her campaign put in a lot of legwork. Former President Bill Clinton stumped for his wife in Phoenix over the weekend and Labor Secretary Tom Perez, a rumored potential running mate for Clinton, campaigned on her behalf in the state.
Sanders, who campaigned in Utah, Idaho and Arizona earlier this week, told supporters in Arizona on Monday night, "Objectively speaking, there is no question that you are looking at the strongest Democratic candidate."
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However his words of encouragement were ineffective in Arizona as he only pulled 37 percent of votes.
Sanders – who was badly in need of a win on Western Tuesday after losing five states to Clinton in last week's primaries – trounced Clinton in Utah with nearly 75 percent of votes and and 18 delegates at only 11 percent reporting.
Clinton entered the evening with a 760-delegate lead over the Vermont senator, but his campaign maintains that he has a better chance of defeating Donald Trump or Ted Cruz in the general election.
Results from Tuesday night's Idaho primary are still pending.