Sen. Bernie Sanders has cut Hillary Clinton’s once-commanding national lead in the Democratic primary race by more than half over the last month, a new Wall Street Journal/NBC News poll finds.

Mrs. Clinton, the former secretary of state, drew support from 53% of people who expect to vote in Democratic primaries, while 42% picked Mr. Sanders. That 11-point spread is much closer than the 25-point advantage Mrs. Clinton enjoyed a month ago, when the poll found her ahead by 59% to 34%.

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