What we don’t know about Clinton and Bush

Political scientists know quite a bit about how U.S. presidential elections work. We generally agree that “fundamentals” such as the economy have a strong effect on elections, and we collectively have a good grasp on how both party nominations and general elections work.

But we don’t know everything! After all, there just aren’t that many presidential elections to use for comparison. That’s especially true of the nominations process, because reforms after 1968 changed it a lot. So new, untested conditions will occur in almost every presidential election cycle.

Here’s a list of some of what we don’t know that might be relevant to 2016:

But we’ve never had anything similar to Jeb Bush’s position – no one has had two unpopular presidents in the family before – so we have no way of knowing how general-election swing voters would react if he was nominated: Would he be seen as a generic Republican, or is the Bush name poison for some who would otherwise consider the party’s nominee?

So far, Rob Portman and Mitt Romney have been eliminated. I’d bet that only a handful of the strong contenders will survive into 2016, and that the contest will have a solid structure by then. Yet there hasn’t been a similar campaign, especially on the Republican side, since the reforms, so we'll have to see how they handle it.

I could add an item on the post-Iowa winnowing. I think the evidence shows that parties have become good at rapidly reducing the number of viable candidates and preventing the others from affecting the outcome. But other political scientists are less confident that voters will follow what parties decide. Some suggest that new campaign-finance arrangements will allow losing candidates to stay in when in the past they would have dropped out. That, too, will be tested in this cycle.

One more: Does it hurt a party to fight hard over its nomination while the other party settles on a candidate early? Some argue that contested primaries hurt a party by wasting resources and making it harder to unite for the general election. Others believe contested nominations energize the party. Overall, the evidence is mixed. Either way, the effect appears to be small. Still, we have a bit of uncertainty on this one.

All in all: The Monkey Cage and Mischiefs of Faction and FHQ and other sources for what political scientists know are going to be excellent guides for WH 2016. But it’s important for us to tell you what we don’t know, too.

Jonathan Bernstein is a Bloomberg View columnist covering U.S. politics.