NEW YORK --A new CBS News poll out Thursday shows Democrat Hillary Clinton would beat Republican Donald Trump by 10 points in a head-to-head match up.

Clinton would defeat Ted Cruz by three points. The only Republican candidate who would beat Clinton is John Kasich.

Bernie Sanders does Clinton one better: He would beats all the Republicans -- Trump, by 17 points.

The Democratic candidates are debating in Brooklyn Thursday night, five days before the New York primary.

Sanders drew one of the largest crowds of his campaign Wednesday night, more than 15,000 people in Greenwich Village. But he admitted Clinton still has the edge.

"This is a tough race for us," Sanders said.

Clinton's large lead in pledged delegates is poised to grow next Tuesday, which has Sanders supporters increasingly eyeing superdelegates -- the roughly 700 party officials who overwhelmingly back Clinton, but are free to switch.

One Sanders supporter even posted a "superdelegate hit list" online, complete with names, email addresses and phone numbers.

Akilah Ensley is one of many superdelegates who say they've been deluged with hostile Facebook messages and emails.

One message Ensley received said, "How in the hell can you sponsor Hillary over Bernie? You should be ashamed of yourself."

"There's been some rude names used, there's been kind of a knock at my character and my intelligence, as to why I would be supporting someone that they see as the establishment," Ensley told CBS News.

The Sanders campaign says it doesn't employ those tactics or condone them. Aides are working quietly to woo superdelegates, but would need to convert hundreds of them to make a difference.

Jane Sanders told CBS News digital journalist Kylie Atwood that the superdelegate system should be eliminated altogether.

"We think the rules are ridiculous," Jane Sanders said. "What it is is an insurance policy for the establishment to make sure they don't get somebody they don't want."

Since their creation in 1982, superdelegates have never subverted the popular vote and don't appear poised to do so now.

Typically they only switch sides when the early front-runner they backed gets overtaken in the primaries, as Clinton was by then-Senator Obama in 2008.