Down-Ballot Coattails Drag

Overview

This pillar quantifies the negative 'coattails effect', where an unpopular candidate at the top of a ballot reduces votes for other candidates in the same party. It helps identify races where a party might underperform due to a weak standard-bearer.

What It Does

It analyzes the polling gap between different candidates of the same party in the same geographic area, such as a presidential and a senatorial candidate. This is combined with historical data on how frequently voters in that area split their ticket. The pillar synthesizes these factors to produce a 'drag score' that predicts potential underperformance.

Why It Matters

Markets often focus on individual races in isolation. This pillar provides an edge by revealing systemic weakness across a party's ticket, allowing for more accurate predictions on vote margins and upsets where a seemingly strong local candidate is vulnerable.

How It Works

First, the pillar aggregates recent polling for top-of-ticket and down-ballot candidates in a specific state or district. It then calculates the 'favorability gap' between them. This gap is weighted against the region's historical split-ticket voting index. The final output is a score indicating the likely percentage point drag on the down-ballot candidate.

Methodology

The core calculation is the Drag Score = (Top-of-Ticket Polling Avg - Down-Ballot Polling Avg) * (1 - Historical Split-Ticket Index). Polling averages are calculated using a 30-day trailing window of all available polls. The Historical Split-Ticket Index is the percentage of voters who voted for different parties for President and Senate/House in the prior two election cycles for that jurisdiction.

Edge & Advantage

It provides a contrarian signal by identifying hidden weaknesses in a party's slate that single-race polling and analysis often overlook.

Key Indicators

• Candidate Favorability Gap

  high

  The percentage point difference in net favorability ratings between the top-of-ticket candidate and a specific down-ballot candidate.

• Split-Ticket Propensity

  medium

  A historical index measuring the tendency of a state or district's electorate to vote for candidates from different parties on the same ballot.

• Down-Ballot Undervote Rate

  low

  The historical percentage of ballots in a district with a vote for the top race but not the down-ballot race, indicating voter disengagement.

Data Sources

• FiveThirtyEight Polling Aggregates

  Provides aggregated polling data for federal and statewide races, used to calculate favorability gaps.

• MIT Election Data and Science Lab

  Offers historical precinct-level election results to calculate split-ticket voting and undervote rates.

• The Cook Political Report

  Provides expert analysis and race ratings which help contextualize the potential impact of a drag effect.

Example Questions This Pillar Answers

• → Will the Republican candidate for Senate in Arizona outperform the Republican presidential candidate's margin in the state?
• → What will be the final vote margin in the Pennsylvania Senate race?
• → Will the Democratic candidate win the House race in Ohio's 9th congressional district?

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