Ezra Klein tells us today that candidates take campaign promises seriously. I haven't reviewed the research, but it is easy to identify some important campaign promises that President Obama made over the course of his campaign that he clearly has not taken seriously while in office.
His pledge to renegotiate NAFTA was important in gaining support from manufacturing workers in many key primary states. This pledge was clearly never taken seriously once he got in the White House.
President Obama also promised to push for legislation that would allow for judges to rewrite the terms of home mortgages in bankruptcy. Any effort in this direction has been all but invisible since he entered the White House.
Finally, the public option portion of his health care plan clearly was not a priority for his administration. While he would have signed a bill that included a public option, he made it clear that he did not view it as an essential part of the plan.
Obviously there are promises that candidates feel little qualm about abandoning once they take office.