Clinton on track to capture Democratic nomination

If Clinton does as well as expected in next week's primaries, she's on track to clinch the nomination with help from superdelegates, the party insiders who can back either candidate, on June 7.

"The race for the Democratic nomination is in the home stretch, and victory is in sight," she told supporters at her victory party in Manhattan on Tuesday night.

Clinton added 33 new endorsements from superdelegates over the past month, according to a new Associated Press survey, expanding her already overwhelming support, despite Sanders' recent string of victories in Wisconsin and the West.

Some say privately that they don't want to make their support public because they fear aggressive online attacks from certain Sanders backers, who've harassed some superdelegates with threatening calls and emails.

The Sanders campaign contends that if he can close the gap with Clinton among delegates chosen in primaries and caucuses, the superdelegates will flock to his side to avoid overturning the will of the party's voters.

Both campaigns had cast the New York primary as one that would either put Clinton on a clear path to the nomination or bolster Sanders after a string of primary wins.

Robby Mook, Clinton's campaign manager, said Sanders must decide whether he wants to continue to "make casualties" of the likely nominee and the Democratic Party.