NEW HAMPSHIRE—Tonight, President Obama will address Congress and the nation in his 2012 State of the Union address. The SOTU has become both an important civic and political ritual and a signal about the administration’s policy priorities for the coming year. However, the drama of a televised presidential speech also encourages hype by political reporters who have been taken in by the myth of the bully pulpit.

Politico’s Carrie Budoff Brown and Glenn Thrush, for instance, led their story on the State of the Union with the claim that “The Republican candidates… are about to get a sharp lesson in the power of the presidency.” But as Bloomberg’s Al Hunt pointed out in a column published locally in the Concord Monitor, “Obama’s speech before a joint session of Congress is likely to prove as ephemeral as those of these predecessors.”

In particular, the evidence is clear that presidents don’t tend to get a “bounce” in approval levels from the SOTU. These findings reflect a more general misperception. Despite what many reporters believe, the president can rarely change public opinion on domestic policy with this or any presidential address.

However, rather than wait for post-SOTU polling to determine if the president’s approval numbers have changed, many media outlets use scientifically dubious instant polls of people who watched the speech. These are not a valid representation of public opinion since the speech audience is a self-selected group and contains a disproportionate number of supporters of the president (because those who like the president are more likely to tune in). In addition, it may be difficult to contact people quickly; polls typically take several days to complete in order to allow time to call people back who do not answer.

As John Sides and I argued in an article (PDF) in the political science journal The Forum, a better approach for reporters would be to take what is essentially the opposite angle from the Politico lede quoted above and use the finding that SOTUs rarely create a “bounce” to draw out the challenges that Obama faces given his inability to change public opinion with this speech. Reporters could also investigate how decisions were made within the administration about the policy priorities in the address and how those are likely to contrast with the positions taken by the Republican candidate in the general election. At a minimum, though, both national media outlets and those here in New Hampshire should try to avoid covering instant poll results or at least provide proper context about their scientific validity.

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Brendan Nyhan is an assistant professor of government at Dartmouth College. He blogs at brendan-nyhan.com and tweets @BrendanNyhan.