In the paper's Wednesday edition, the editorial board which endorsed Clinton's White House bid earlier this year says the New York senator's "negativity" is doing "harm to her, her opponent, her party and the 2008 election."

"The Pennsylvania campaign, which produced yet another inconclusive result on Tuesday, was even meaner, more vacuous, more desperate, and more filled with pandering than the mean, vacuous, desperate, pander-filled contests that preceded it," the board writes.

The paper finds fault in Clinton's latest campaign ad, which includes an image of Osama bin Laden, and asks, "Who do you think has what it takes?"

"Mrs Clinton became the first Democratic candidate to wave the bloody shirt of 9/11," they write, adding that it is a tactic that is "torn right from Karl Rove’s playbook."

"Mrs. Clinton does more than just turn off voters who don’t like negative campaigning," the editorial also states. "She undercuts the rationale for her candidacy that led this page and others to support her: that she is more qualified, right now, to be president than Mr. Obama."

The paper also says Barack Obama deserves some of the blame for the negative tone. "He is increasingly rising to Mrs. Clinton’s bait, undercutting his own claims that he is offering a higher more inclusive form of politics."

But the editorial makes clear the paper thinks most of the blames lies with Clinton. "If she is ever to have a hope of persuading [superdelegates] to come back to her side, let alone win over the larger body of voters, she has to call off the dogs."