Stimson's data suggest that Reagan's election was a reflection, rather than a cause, of growing anti-government sentiment. Once Reagan took office and began to enact his agenda to reduce the size and scope of government, however, public demand for government actually grew, reflecting the thermostatic pattern Stimson documents. In other words, rather than decreasing demand for big government, Reagan's presidency actually increased it.Nyhan's main lesson for Obama seems to be: stop suggesting that you plan to move public opinion from the bully pulpit, because Reagan was not able to do it once he was in office. I would add, without falling into an assumption that history will mechanically repeat itself, that the Reagan pattern suggests that Obama may have already not "changed the trajectory" of American politics, but ridden the change induced by George W. Bush's massive failures to effect about as much legislative change as the electorate will tolerate at one gulp.
The pattern seems to be: a failed president generates an appetite for change; a politician and/or party who best channels that appetite gets elected; the electoral sweep enables to a measure of legislative success, which quickly makes the electorate queasy and leads it to repudiate the president's party at the polls; either good luck or good effects of the policy shift or both kick in after the president's first midterm, leading to reelection. This pattern describes Clinton's presidency as well as Reagan's.
*Hat tip to Jonathan Bernstein)