The presidential bully pulpit isn’t as effective as one would think. Evidence shows that the louder a president speaks to support an issue or bill, the more committed the opposing party will be to ensure that it won’t pass:
To test her theory, she created a database of eighty-six hundred Senate votes between 1981 and 2004. She found that a President’s powers of persuasion were strong, but only within his own party. Nearly four thousand of the votes were of the mission-to-Mars variety—they should have found support among both Democrats and Republicans. Absent a President’s involvement, these votes fell along party lines just a third of the time, but when a President took a stand that number rose to more than half. The same thing happened with votes on more partisan issues, such as bills that raised taxes; they typically split along party lines, but when a President intervened the divide was even sharper.