Labor and progressive leaders are threatening House Democrats who oppose health care legislation with potentially destructive third party challenges in November…

In districts where Democrats vote “no,” voters “will have the Republican against health and the Democrat against health care, and they’re going to ask themselves, ‘Where’s the candidate that shares my values,’” Stern told POLITICO. “A lot of us would like to run another candidate.”

“I am not the only labor leader looking at [the question of] what is the price of betrayal,” he said, suggesting that Pennsylvania and Illinois could also see liberal third party challenges…

“There is, for the first time in American history, a real chance for a third party,” said Stern, who argued that the same discontent that has inflamed a new conservative grassroots could drive a liberal outside challenge.