Context:

NBC News polling averages synthesize multiple national surveys to chart public opinion over time, weighting more informative and precise polls while damping outliers. The method standardizes results across populations (all adults, registered voters, likely voters) and populations patched to a common baseline of registered voters to produce a single, smoother average. It includes NBC’s own polls and explains how polls are selected, weighted, and adjusted to prevent overrepresentation by frequent pollsters or biased samples. The approach emphasizes non-predictive framing, transparency about methodology, and clear separation of trends by population and party identification. The piece also notes the practical differences between presidential approval and generic congressional ballot tracking and progress toward post-Labor Day shifts to likely-voter samples for context.

Dive Deeper:

• The NBC News polling averages aim to measure changes in public opinion over time rather than predict outcomes, and they combine national polls using a weighting system that favors more informative surveys while reducing random variation.

• Inclusion criteria require polls to disclose field dates, sample size, and margin of error; if such information is missing, the poll is excluded from the average, and polls from the same survey population aren’t double-counted.

• Averages are anchored to registered-voter polls as the baseline, with adult and likely-voter polls adjusted to align on the same scale using paired results from surveys that report multiple populations.

• If a poll reports multiple populations, only one result is entered into the average, prioritizing registered voters, then all adults, then likely voters, while preserving transparency by listing all populations in the full poll list.

• To maintain stability, the model downweights older polls and those with larger margins of error, and it limits the impact of surprising results unless corroborated by other data, smoothing the published average to highlight sustained shifts.