When the public supports the president's position...then what?

I have learned from political scientists including Brendhan Nyhan and Jonathan Bernstein that presidents generally can't sway public opinion via appeals from the bully pulpit.  National Journal report George Condon, relaying the thoughts of political scientist George C. Edwards III, encapsulates the accepted wisdom:

“It is true for all presidents. They virtually never move public opinion in their direction,” Edwards tells National Journal. Citing polling numbers for six decades and multiple presidents, he says, “It happened for Ronald Reagan. It happened for FDR. It happens all the time. You should anticipate failure if you’re trying to change people’s minds. The data is overwhelming.” What Edwards learned is that presidents succeed in rallying the public when the public already agrees with them.

With regard to Obama, however, Edwards' cited examples do not fit his categories. His analysis -- perhaps sharply abbreviated by Condon -- glides over the ambiguities involved in "rallying the public when the public already agrees":