September fundraising

Updated October 21, 2026. The forecast now uses cumulative receipts through September 30 for 24 matched Senate races. The adjustment remains provisional and is capped at three margin points.

I compare two-year candidate receipts, retaining each campaign’s actual reporting start date. Total receipts include transfers and candidate financing; outside spending is separate. Unmatched, independent-axis and unpolled races receive no additional financial adjustment.

Historical comparison

Using the same 142 historical candidate pairs across six elections, September receipts changed average margin error from 4.891 to 4.857 points; June gave 4.862. Each election has equal weight. The September gain is small and not statistically reliable (paired election-level p=0.41). Probability error is almost unchanged from the baseline and worse than the June comparison.

The formula learns from earlier elections, allowing for partisan lean, incumbency and prior results. Only the additional fundraising information is applied, once, before candidate-history and scandal adjustments. Existing uncertainty ranges are retained.

Current race effects

Positive changes favor the Democrat. These are margin points, not changes in win probability.