Clinton leads Sanders by 5 points, 50 percent to 45 percent, in the latest survey. By comparison, the same poll from February showed her with a 10-point lead.

Clinton took the next step on her path toward locking up the Democratic nomination with a win in New York last week, and is the favorite in polls from several Northeastern states voting Tuesday.

Despite her big lead among delegates — who will ultimately determine the nominee — Sanders, a self-described democratic socialist, continues to be popular in national polls.

The Suffolk poll is one of several recent national surveys that have found Clinton's once-massive advantage over the independent Vermont senator down to single digits.

The survey also shows a disparity between supporters of the candidates over how fair they feel it would be if their pick didn't win the nomination.

A majority, 51 percent, of Clinton voters said it would be fair if she lost the nomination, compared with just 28 percent of Sanders supporters.

Most Clinton supporters, 52 percent, said Sanders should withdraw from the race if Clinton locks up the nomination before the convention, though 39 percent said he should stay in the race.

Among Sanders supporters, 21 percent said he should withdraw in that scenario, while the overwhelming majority — 71 percent — said he remain in until the convention regardless.

The survey of 363 likely Democratic voters was conducted April 20-24 via landlines and cellphones with a margin of error of 5.1 points.