Brendan Nyhan observes that while you can probably see the impact of Obama’s health care speech in public opinion on the issue, what you’re seeing is a lack of any lasting impact:
This, however, isn’t some odd scenario. It’s exactly what normally happens:
I’m emphasizing this point because there’s a misperception among journalists that the president can easily move public opinion. As we’ve seen again and again over the years, it’s simply not true, but the lack of followup by the press means that the lesson is never learned. (At most, a failure to move poll numbers is blamed on some specific aspect of president’s message or strategy.) So we repeat the same cycle over and over again.
I think this is a pretty insidious aspect of our political culture. It’s not just that media commentary overemphasizing the president’s ability to shape opinion is inaccurate, it has a really detrimental impact on people’s ability to organize and effect political change. People are strongly encouraged to believe that the key to achieving policy change is to elect a president who’s friendly to their views. Then when that turns out to be insufficient they don’t move on and do additional organizing in House and Senate races. Instead, they tend to become frustrated with the president they worked to elect. But why blame the victim of congressional obstruction rather than the perpetrator? Well, people always seem to find a way to tell themselves, if only the president had fought harder he would have gotten it. He must have lost because he didn’t really care.
In the real world, presidential preference-intensity and arm-twisting and such does matter. Some. But it only matters some. And in particular, people grossly overestimate the ability of the president to unleash some kind of public opinion tidal wave that forces congress to act.