The Democrats in unsafe seats are challenging him on proposed programs and initiatives that are unpopular in those Democrats' districts. They are not willing to incur the wrath of their constituency just to support Obama. But they are challenging the initiatives on the basis that their constituency is not yet ready to accept it. They are not challenging the intiatives on the basis that the premise for support of them is wrong or is flat out misrepresented.

And, they are in a small minority.

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Socialism in general has a record of failure so blatant that only an intellectual could ignore or evade it."
-- Thomas Sowell

" I am for doing good to the poor, but I differ in opinion of the means. I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it."
-- Benjamin Franklin, On the Price of Corn and Management of the Poor, November 1776