An Ohio-based group of Clinton supporters has announced it will actively work against Barack Obama if he becomes the nominee for the party, saying Senator Clinton has had to fight gender discrimination from party leaders and the media.
Organisers Cynthia Ruccia, 55, and Jamie Dixey, 57, say they are organising women, men, minorities, union members and others in Ohio, Pennsylvania, Florida and Michigan - all important swing states in November - to protest at Senator Clinton's treatment.
"We have been vigilant against expressions of racism, and we are thrilled that the society has advanced that way" in accepting Barack Obama as a serious candidate, Ms Ruccia told online political magazine Politico.
"But it's been open season on women, and we feel we need to stand up and make a statement about that, because it's wrong."
In a press release, the group said: "We have a plan to campaign against the Democratic nominee. We have the (wo)manpower and the money to make our threat real. And there are millions of supporters who will back us up in the swing states. If you don't listen to our voice now, you will hear from us later."
As calls grew for Senator Clinton to quit the race, Ms Ruccia said women felt "we're being told to sit down, shut up, and get with the program".