We’ll be reporting from Cleveland all week and live-blogging each night. Check out all our dispatches from the GOP convention here.

Welcome, class, to Conventions 101. If you’re looking for Conventions 201, you’re in the wrong place; please see Professor John Sides down the hallway. And put those cellphones away, please. We’ll get to the drama created by Ted Cruz on Wednesday night in a moment, but let’s start with the basics. For instance, as far as we’re concerned, conventions serve two major functions:

Conventions serve to unify the party. Conventions, literally speaking, are party meetings. At its convention, a party nominates candidates for president and vice president, along with taking care of other party business, such as establishing rules for future nominations. Conventions are showcases for the presidential ticket. All the major broadcast and cable networks cover the conventions extensively, giving parties the equivalent of hundreds of millions of dollars in media exposure. In contrast to other sorts of political events, the media generally lets the parties set the program, and make their case to the American public in a relatively uninterrupted way. It’s a unique, once-per-cycle opportunity.

Put another way, conventions are both the official end of the nomination process and the unofficial beginning of the general election process. In the modern political era, nominations are usually decided well ahead of the conventions, so they can come to resemble extended infomercials instead.

Still, these functions can sometimes come into conflict. If you watch only the prime-time coverage of conventions, the parties generally put on a good show. But at odd hours, there can be disputes on the convention floor. Or the party will put on speakers who present red meat to the party faithful, or who fulfill obligations to party constituencies, that it wouldn’t necessarily want swing voters to see.

But modern conventions are generally successful events. They almost always produce polling “bounces” in favor of the party that just held them. These bounces can be short-lived and aren’t always predictive. Still, some part of the convention bounce usually sticks, and polls taken a few weeks after the conventions are generally much more accurate than those taken a few weeks beforehand.

At a minimum, the parties almost always succeed at converting some undecided voters, who are leaning toward the nominee but who aren’t yet fully committed, into their column. So Hillary Clinton wants to persuade straggling Bernie Sanders supporters (and there are still quite a few of them) to join her cause, and Donald Trump wants to do the same for supporters of Cruz and other Republican candidates. Ideally, they’ll also bring some swing voters along. But if the nominees can’t achieve some modicum of party unity, the convention is a potential disaster.

So from a Conventions 101 standpoint, what happened in Cleveland on Wednesday night was a potential disaster for Trump and the Republicans. Cruz, the second-place finisher in the primaries, conspicuously refused to endorse Trump, and left the stage to a chorus of boos. An unusually large number of Republicans have also declined to endorse Trump, including Ohio Gov. John Kasich, who isn’t appearing at the convention even though his state is hosting it. But those defections might be forgotten about for a few days, provided that the party put on its best face in Cleveland. Cruz’s refusal to endorse Trump, however, which he seemed to draw out for emphasis to embarrass Trump, took place at center stage. It was bad from both a uniting-the-party standpoint and from a showcasing-the-ticket standpoint. It was among the most dramatic events that we’ve seen at a convention in recent years.

If you sneak into Conventions 201, you’ll find that the story is more complicated. We don’t have all that much data on what makes for successful conventions and what doesn’t, and convention bounces aren’t always that predictable. Some conventions that are remembered as disasters, such as the 1972 Democratic convention, did produce minimal or even negative bounces for their parties. But Jimmy Carter got a fairly large bounce out of the 1980 convention, even though Ted Kennedy was defiant toward him, one of the better precedents for what happened on Wednesday.

Conventions 201 might also encourage you to think carefully about distinguishing correlation from causation. Is it the conventions themselves that matter, or that they provide a leading indicator about how the rest of the campaign might go? Barack Obama didn’t get much of a bounce after his 2008 convention, which was well-staged but felt like an anticlimax after his dramatic victory in the Democratic primaries — whereas John McCain and Sarah Palin made a big splash. But Palin soon turned from a positive into a negative influence for the GOP ticket, and Obama’s campaign performed very well down the stretch run. From that standpoint, this year’s RNC has been problematic not only because Trump is squandering an opportunity to put on his best face for the voters, but also because he’s made a lot of unforced errors, suggesting that his campaign might struggle in all sorts of ways from now through November.

Again, none of this is necessarily all that predictable. For all we know, Trump will deliver the speech of a lifetime on Thursday night and be up 7 percentage points on Clinton by the weekend. Our strong preference is to take a wait-and-see approach, and it will be a few more days before we can comfortably measure the magnitude of Trump’s bounce.

But if you believe that campaigns make a big difference — the empirical research is a bit mixed on that, by the way — the first three days of the convention are the latest and surest sign that Trump and his campaign have profound problems, which could make it hard for them to win even if geopolitical events break in their favor. Conventions are fairly often the pivot points in presidential elections, and the first three days haven’t gone well for Republicans.





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