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The general election starts now. Here's how to read the polls.

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Hillary Clinton, Bill Clinton, and Tim Kaine campaigning in Pennsylvania on Thursday.
Hillary Clinton, Bill Clinton, and Tim Kaine campaigning in Pennsylvania on Thursday.
Justin Sullivan/Getty Images

PHILADELPHIA — The balloons came down, the speeches ended, and now the convoy is packing up and heading out onto the campaign trail.

The general election is on.

The race is in a weird moment. Right now the polls between Hillary Clinton and Donald Trump show an election that’s reasonably close — Trump is up by 0.9 points in RealClearPolitics’ polling average, the aggregator that most election watchers regard as the best way to gauge the state of the race.

But most observers also expect that polling closeness to prove fleeting. Trump appears to have benefited from a polling bump after the Republican National Convention, and Clinton is also expected to get a post-convention bump after Friday’s conclusion of the Democratic National Convention. (It normally takes a few days in the polls — which have to be conducted and released — to show up in the polling aggregators.)

So while Trump and Clinton look like they’re running neck and neck, most analysts say we should probably wait for the dust to clear from the conventions before reading the race. Once that happens, we’ll begin to get a much clearer picture of where the candidates are at the starting gate.

Why you should wait until after the post-convention polling bump

Now, just like some people overinterpreted Trump’s convention polling bump (including Trump himself), some may overinterpret Clinton’s.

Clinton had a 4-point lead on Trump before the conventions began. Alan Abramowitz, an Emory University political scientist, told me Friday he’d be skeptical of any polling that comes out next week that shows her not only erasing Trump’s convention polling bump but dramatically expanding her pre-convention lead.

One reason the conventions traditionally bump a candidate’s polling is because they tend to increase the likelihood that people who already supported them will respond to a pollster. That doesn't mean people are changing their minds — just that the pollsters are more likely to hear back from, and thus include, those favorable responses. That dynamic is the case now more than ever, because polling response rates in general have gotten much worse over time, according to Abramowitz.

"There’s reason to believe a lot of these fluctuations are kind of artificial and difference of response rates to pollsters rather than real shifts in how people are thinking," Abramowitz says.

The conventions make party voters suddenly proud to declare their support for the nominee. But that spike in pride dissipates, and we’re soon left with response rates not temporarily ginned up by the excitement of the conventions. Those are the ones to look for to parse what's happening in November.

Abramowitz, like most other election junkies, thinks it probably makes more sense to wait until mid-August to wait for this temporary effect to fade. That’s a pretty standard view — even if it doesn’t do much to stop people from obsessing over the latest poll.

What to look for in convention polling

Now, the polls aren’t entirely useless during the convention period. They won’t necessarily tell us who will win the election, but there are some interesting things to watch.

For example, one explanation political scientists like to offer for the convention polling bump is the imbalance of news coverage: Attention to each candidate surges during that period.

Here’s John Sides, a political scientist who writes for the Washington Post:

Conventions generate a larger "dose" of information than is provided by the daily ebb and flow of news coverage. Thomas Holbrook’s study of campaigns from 1984-92 found that front-page coverage of each presidential candidate rose sharply during his party’s convention.

A second reason is that the news coverage during the convention favors the candidate being nominated. There are typically no increases in the coverage of the Republican candidate during the Democratic National Convention, and vice versa.

But why does the wall-to-wall coverage boost a candidate’s poll numbers? Georgetown professor Jonathan Ladd says the glut of information in turn serves to remind voters about what party they belonged to in the first place.

Most people aren’t political junkies, and they don’t pay all that much attention during the primaries. So the conventions remind those people which party they’ve traditionally voted for, and why. That’s what helps account for the polling surges.

"Conventions appeal to those with some affiliation or affection for that party," Ladd says. "The conventions are when the parties get ready for the fall."

This is how you should interpret convention polling: by looking to see if Clinton and Trump were able to consolidate their parties’ supporters behind them.

It looks like Trump was able to do just that, increasing the percentage of Republicans who say their party is unified by 8 points in CNN’s polling.

Will Clinton do the same? We’ll be able to look at post-polling this week to help us find out — even if it doesn't amount to a perfect reflection of where the country as a whole really is.

When do I pay attention again?

Political scientists Robert Erikson and Christopher Wlezien, authors of the book The Timeline of Presidential Elections: How Campaigns Do (and Do Not) Matter, are widely regarded as the top authorities on general election polling.

And one thing their data from 1952 to 2008 clearly shows, according to Princeton election expert Sam Wang, is that head-to-head polls from January through April tend to be better predictors of the eventual winner than polls from May through July.

That’s relatively good news for Clinton, since she led Trump by a substantial margin during this early period, although polls this autumn will give us an even better sense of the race.

Nobody knows exactly why the polls suddenly become screwy and less predictive during the summer. One possibility is that there are still a lot of bad feelings lingering within each party after primaries: Supporters of the losing candidates sometimes say they’ll refuse to support the party nominee for a spell. These holdouts typically come around in time for the general election, but they can obscure what’s happening in the summer. This also tends to be when the conventions are held, causing those temporary ups and downs in polling.

Still, despite the weirdness of polls around the conventions, they’ve historically proven pretty accurate as we head into fall and Election Day draws near.

Here’s a chart from Erikson and Wlezien that shows how the polls grow increasingly predictive after August:

We’re about 100 days from Election Day right now. In a few weeks, according to Erikson and Wlezien's research, general election polling will be much more predictive of the result in November. (The higher the green line in the chart above, the more predictive polling from that date forward has proven.)

"The polling averages just don’t move much more than 2 or 3 percentage points after the conventions," Ladd says. "Especially since the conventions are in July, the person in the lead in August will have a really good chance of winning."

That’s why Kathy Frankovic, the former CBS polling director and analyst at YouGov, says she once tried to follow a simple rule: Don’t check the polls until Labor Day.

"Otherwise, you're spinning wheels. You're worrying — or celebrating — prematurely," she says.

The bad map we see every presidential election

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