Part 1: The Model | Vanda’s three-part US midterms series
Vanda’s election model favours Democrats taking the House. The Senate remains a much closer contest.
The uncertainty is not simply whether voters are turning against Republicans. It is whether those voters switch sides or stay home.
Vanda Macro Intelligence’s proprietary election model assigns Democrats a 78% probability of winning the House, according to research published on 21 October. Whether Democratic momentum delivers control of both chambers depends on how it translates into competitive races, and who actually turns out.
A model built around the races that matter
In his research, Wouter Jongbloed sets out Vanda’s proprietary election model, combining detailed assessments of competitive House districts and Senate races with 40,000 simulations to account for uncertainty across the broader electoral map.
The approach examines how individual contests and a shared national swing could shape control of Congress. It provides a way to test how far a favourable Democratic environment might travel, rather than assuming the same shift everywhere.
The research also compares the model’s evolution with betting-market odds, examining how each responds to new information. Those markets provide a useful reference, but concentrated participation and sentiment can influence their pricing.
Turning against Republicans is not the same as voting Democrat
Disaffected Republican voters are a central uncertainty. Some may switch their support to Democrats. Others may abstain. Both reflect dissatisfaction with the administration, but they can produce different results in closely contested races.
A shift in reported preferences therefore does not necessarily translate into an equivalent shift at the ballot box. The strength of a Democratic wave depends partly on whether those changing preferences become votes.
For the Senate, where control hinges on a smaller set of competitive contests, that distinction could be decisive.
The balance of power beyond election night
A Democratic victory in the House would change the balance of power in Washington. But the scale of any shift, and whether Democrats also capture the Senate, could prove more important for the policy outlook than the headline result itself.
How would different Congressional outcomes constrain the White House? And which changes would matter most for financial markets?
Those questions require looking beyond a single election probability to the composition of Congress and the policy dynamics that follow.
What is Vanda’s model seeing beneath the headline probabilities?
Wouter Jongbloed’s full research examines how the model responds to new information, where its assessments differ from betting markets and which competitive races could determine Congressional control.
To access the full analysis, contact sales@vanda.com.
Next in the series, Part 2: The Money. Can money break a political wave?
