Modest national poll bias can flip Senate

Using FLIPR simulations, the article shows that a 3–4 point systematic poll error in one direction across states — an error size that has occurred before — could change whether Democrats secure a Senate majority or leave control split 50‑50. Nate Silver explores both directions (polls overrate Democrats or Republicans) and identifies tipping states and the sensitivity of outcomes to small national biases. — If journalists, campaigns, and voters misread national polling as precise, they may misallocate resources, mislead turnout expectations, and produce misleading narratives about mandate or momentum in a way that materially affects election results.