A thermometer or a thermostat

I’ll put it this way, brother: You’ve got to be a thermostat rather than a thermometer. A thermostat shapes the climate of opinion; a thermometer just reflects it. If you’re just going to reflect it and run by the polls, then you’re not going to be a transformative president. Lincoln was a thermostat. Johnson and F.D.R., too.
— Cornell West, answering the question “How can Obama be the president you want him to be when he’s facing this Republican Congress?” From Talk - Cornel West - NYTimes.com, Sunday, July 24, 2011. (It also reminds me of “Are you the scanner or the barcode” by Cory Doctorow from Make volume 22 http://makezine.com/22/ — the article is not online.)