Sanders, 74, now has support of 47 percent of Democratic primary voters as against 44 percent people who back Clinton.

A month ago, Clinton, 68, had support of 49 per cent of the Democratic primary voters.

And last summer, Clinton had a lead of 46 points and that of 22 points as recently as two months ago.

This is the first time that Sanders is leading a national poll against Clinton, who not long ago was regularly described as the 'presumptive' Democratic nominee, according to the poll ahead of the South Carolina primary on February 27.

Clinton, however, continues to lead in South Carolina where the Democratic primary is scheduled for later this month. But her lead with Sanders has reduced.

Likely Democratic primary voters favor Clinton over Sanders by 28 points (56-28 per cent), the poll said.

In December, Clinton held a 44-point lead (65-21 percent). On the Republican side, front runner Donald Trump leads with 36 percent support from Republican primary voters.

He is followed by Texas Senator Ted Cruz with 19 percent and Florida Senator Marco Rubio 15 percent.

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