Why Biden’s National Lead Over Trump Narrowing in RCP Polling Average, But Steady in FiveThirtyEight’s
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Former Vice President Joe Biden’s national lead over President Donald Trump has dropped by three points in the RealClearPolitics average recently, but has remained relatively stable at around eight points in the FiveThirtyEight tally.
Since July 26, when Biden’s lead in the RCP average was 9.3 points, the national race has narrowed by almost three full points, with Biden now leading Trump 49.1 percent to 42.7 percent.
But in the FiveThirtyEight national average, Biden’s lead has remained steady over the same time period, dropping a mere .4 percent since July 26.
Neither average should be ignored, but it’s important to understand the differences between the two. RCP calculates its average by looking back at the previous two weeks of qualifying polls, and producing a raw, unweighted average.
This has advantages and disadvantages, but over the most recent period, it means Biden’s average could be getting dragged down by a larger number of polls using a “likely voter” model, which tend to favor Trump. Nearly half of RCP’s qualifying polls over the past two weeks have used a “likely voter” model.
The FiveThirtyEight average uses a more complicated formula that weights results based on the pollster ratings, sample sizes, and state polling results, which produces a more stable average that theoretically gauges public opinion more completely.
But that doesn’t mean one or the other should be dismissed out of hand. The more volatile RCP average can cause headaches with bad headlines and amplify the effects of outlier polls, but can also more quickly identify a potential trend than the more stable FiveThirtyEight average.
A look at Biden’s performance in the individual polls that make up RCP’s average, though, show a much more stable lead. Apples-to-apples, he’s steady in most of them.
Trump’s approval rating in both averages paint a picture closer to FiveThirtyEight’s current snapshot, showing Trump has enjoyed a modest rally of about one point in the past few weeks.
