Well technically, last week’s Republican National Convention had less impact than any party convention that Gallup has ever measured.
Since 1984, Gallup has polled voters following each party convention asking whether what they saw or read of the event made them more likely or less likely to vote for that party’s candidate. Subtracting the “less likely” tally from the “more likely” result measures the convention’s net impact on voters.
Nationally, the net effect of last week’s GOP convention was +2, with 40% of respondents more likely to vote Republican afterwards and 38% less likely. That compares to a +5 effect for the 2008 RNC that nominated John McCain and a +3 effect for the 2004 convention that renominated George Bush.
That said, Gallup found that the 2012 RNC played slightly better than the national average among voters self-identifying as independents, with a +3 effect. Pundits already predicted minimal movement in the polls following the party conventions this year due to the polarized political climate, where most voters have already made up their minds who they support.
Romney’s speech, on the other hand, stood out for its exceptionally poor reception, says Gallup:
Romney’s acceptance speech this year scored low by comparison to previous convention speeches going back to 1996. Thirty-eight percent of Americans rated the speech as excellent or good, while 16% rated it as poor or terrible. The 38% who rated the speech as excellent or good is the lowest rating of any of the eight speeches Gallup has tested since Bob Dole’s GOP acceptance speech in 1996.
CBS noted of the Gallop polling on Romney’s speech:
Ten percent of respondents also said Romney’s speech was terrible, twice the percentage who thought McCain’s speech, which received the second highest negative rating, was terrible.
However, it should also be said that (as seen in the table below) the net impact of conventions is a poor predictor of election results, since they mark the effective start of the campaign season, and much can happen before election day. The Democratic conventions of 2004 and 2008 both had an equivalent +14 net effect on voters, but the elections had quite different results. And the convention with the second-highest impact Gallup has ever measured was the 1988 DNC that nominated another Massachusetts governor, Michael Dukakis.