Hillary Rodham Clinton was jolted Thursday by the defection of one of her longtime superdelegate supporters, a former national party chairman who urged fellow Democrats to "reject the old negative politics" and unify behind Barack Obama.

A vote for Hillary Clinton is a vote to continue a long, self-destructive Democratic campaign, said Joe Andrew in a letter designed to have an impact on the turbulent race nationally as well as in his home state of Indiana, site of a primary next week.

In response, Clinton told ABC's "Nightline": "I think this has been good for the Democratic Party. ... People can decide however they want to decide. That's up to them."

"But anyone who believes this is bad for the party I just think is not paying attention, because the level of enthusiasm to be part of this process is, from my perspective, helping us build a stronger and deeper Democratic base," said Clinton.

Clinton's hopes of stalling Obama's drive to the nomination rest on a strong showing in the remaining primaries, beginning Tuesday in Indiana. At the same time, she hopes to persuade superdelegates that she would be a stronger candidate for the party this fall against McCain and the Republicans.

In the letter, Andrew not only challenged Clinton's claims about electability, but he also bluntly denounced the type of campaign tactics practiced by some in the Clinton circle.

"If the campaign's surrogates called Governor Bill Richardson, a respected former member of President Clinton's cabinet, a "Judas" for endorsing Senator Obama, we can all imagine how they will treat somebody like me," he wrote.

(Agencies via Xinhua News Agency May 2, 2008)