On the eve of a national Democratic presidential debate in Las Vegas, a CNN/Opinion Research poll of Nevada Democratic caucus-goers shows Hillary Clinton over the magic 50% mark for the early January 19 caucus in the Silver State. Clinton leads Barack Obama by a 51%-23% margin, with John Edwards at 11%.

The other Democratic candidates are still polling in single digits: Bill Richardson (5%), Joe Biden (4%), and Mike Gravel and Dennis Kucinich (1%). Christopher Dodd has less than 1% of the vote in the poll released earlier today.

"Clinton's advantage among Democratic caucus-goers appears to be based on the perception that she is the most electable candidate and the strongest leader in the field," said Keating Holland, the CNN Polling Director.

But Nevada is too close to call in a general election matchup between Clinton and Republican Rudy Giuliani. The poll shows Giuliani leading Clinton, 47%-46% -- a statistical dead heat. Clinton leads another GOP contender, Mitt Romney, by a 51%-42% margin.

"It's not mainly personal qualities that are putting Hillary Clinton over with Democrats," said CNN Senior Political Analyst Bill Schnieder. "It's the view that she's tough. She's experienced, and she's a winner."