The myth of the post-convention poll bounce

TAMPA, Fla. – The convention bounce is the stuff of political dreams.
Buoyed by the love of fellow partisans, lofted by eager anticipation, swaddled and coddled — when was the last time anyone actually asked a tough question of a candidate at their convention, much less had the chance? — the presidential nominee soars heavenward on the wings of celebration.

Then settles back to Earth.

It is not unusual for a candidate to surge in polls in the days after their big party bash. Gallup, which conducts the granddaddy of political opinion surveys, reports that going back to 1964 the average “bounce” yields a 5-percentage point gain in the polls.

That makes sense.

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Imagine a jury trial, in which the prosecution presents its case, followed by the defense. The two political conventions function in much the same way. The out-party goes first, offering all the awful things the incumbent administration has done as proof of why the country can’t possibly survive another four years with that kind of ineptitude in the White House. With that argument fresh in their minds, some loosely moored (politically) or otherwise persuadable voters tip toward the challenger.

Then the party holding the presidency responds and those persuadable voters move back to the undecided column, or even drift to support the incumbent.

It’s these free-floating voters who decide a presidential race.

The partisans — the kinds of people who take a week’s vacation and spend thousands of their own dollars to sweat in the sauna that is Tampa (or Charlotte for the Democrats next week) — are not the kinds of people who need convincing.

All of which is to say, what will most likely happen is a small bounce of some sort for Mitt Romney and his running mate, Rep. Paul D. Ryan of Wisconsin, in polling in the next few days and then a similar, small bump for President Obama and Vice President Joe Biden at the completion of their confab.

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With polls showing only a small slice of the electorate truly undecided, there is not likely to be much spring in either bounce. All of which is to suggest the race, come mid-September, will be right about where it has been for several months now: too close to call, with the state-by-state soundings mattering far more than national horse-race polls.

Of course, you can do yourself a favor and ignore all the incessant polling and just read up on the issues and listen to what the candidates have to say for themselves.

There’s an old cliche with more than a little truth to it: The only poll that matters is the one on election day.

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mark.barabak@latimes.com

Twitter: @markzbarabak