Sen. Bernie Sanders has all but eliminated Hillary Clinton’s polling lead among Democratic voters nationwide, a new Wall Street Journal/NBC News poll has found, offering signs that she continues to struggle with the primary electorate at a time when she wanted to build strength for the general election.

Mr. Sanders for the first time is close to tying Mrs. Clinton, as 48% of Democratic primary voters picked him as their first choice for president, while 50% picked her. In a poll last month, Mrs. Clinton was ahead by nine percentage points, enjoying a 53%-to-44% edge.
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“As she is finishing this primary, she is not gaining strength,” said Bill McInturff, a Republican pollster who conducted the survey with Democrat Fred Yang. “The cracks are showing, and she is losing strength.”
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Mrs. Clinton saw a significant decline in support among white men, younger voters and independents. White men voting in Democratic primaries prefer Mr. Sanders 66% to 32%, up from a 54%-to-41% spread in polls earlier this year. Among voters ages 18 to 49, Mr. Sanders is preferred by 66% to 34% for Mrs. Clinton. She is the preferred choice among older voters by 27 points, 62% to 35%.