In the Democratic and Republican presidential races right now, we’re hearing a lot of claims about electability in general-election matchups.
Ted Cruz says he’s the only Republican who can beat Hillary Clinton in November, while John Kasich is staying in the race because, he maintains, he’s the one GOP candidate who can appeal to swing voters in November. And Bernie Sanders’s campaign argues that he, not Clinton, would be the strongest general-election candidate.
We’re finally getting to the point where, with seven months left to go, general-election polls begin to be meaningful. Yet they can be misleading. How should we read the early numbers?
Political scientists have found that, historically, polls on potential general-election matchups don’t become more reliable in a steady, gradual arc as the months and weeks go by. Instead, after starting off as essentially meaningless, they ratchet up sharply in two steps.
We are just nearing the end of the first stage, when primary and caucus voters first learned about the candidates and formed opinions about them that can be reflected in the November matchups. The second phase occurs at roughly 100 days before the election, corresponding to the parties’ conventions. Once the nominees are known and the general-election campaigns begin, polls do a good job of predicting the outcome.
The polls this year could be somewhat less predictive than usual, because both nominations remain contested. Some partisans who will eventually support their party’s nominee are working hard against that candidate right now, and are focused on all the reasons to oppose him or her. That is why we can expect the winners on both sides to get a boost once they win because the parties will at least partially unite behind them.
Normally the parties will rally around the winner. That will almost certainly be true on the Democratic side this year. As the Sanders campaign has signaled thoughout the campaign, he’ll be a good team player for the fall election.
On the Republican side, who knows? Trump can’t fully unite the party if he wins the nomination, and it’s possible he’ll prevent unity if he loses. And it isn’t clear that Cruz could unite the rest of the party, if he’s the winner, even without Trump throwing bombs from the sidelines. But expect at least some boost for the eventual nominee anyway. The incentives to unite are strong. There’s no way to know what the Republican Party will look like after its convention in Cleveland.
If you believe, for example, that a Trump Republican Party could be united, then you would expect his favorability ratings to move up sharply from their current very low levels.
Voters could also be swayed by new things they learn about the candidates. In the case of Cruz or Sanders, who are still relative unknowns to the general electorate, believe it or not, voters would likely learn more about how ideologically extreme they are, and this would almost certainly hurt them in the general election.
Trump and Clinton are much better known, so new information, on its own, is less likely to change what people think of them.
If you’re looking at polls showing Sanders doing better than Clinton against any Republican contender, just understand that such matchups are inherently untestable. Political judgment is better than polling here.
If you want to look for indicators in the data anyway, trust polling averages, not individual surveys. And focus on the national polling numbers, not the numbers for individual states and the Electoral College. Recent elections featured a relatively uniform swing across states. That is, if the Republican gained two percentage points nationally, he also gained two points in swing-state Ohio, solidly Republican Utah and solidly Democratic Rhode Island.
The candidate who wins the popular vote will almost certainly win the Electoral College. For now — and until October — focus on how the national vote is shaping up. And state polls are a distraction until then.