How will Undecided Voters Break in the PA Senate Race?

Photo Credit: Office of Former United States Senator Claire McCaskill


By Logan Phillips
Date: September 30th, 2022

Republicans need to flip just one seat to take the Senate in 2022, but Democrats could make their task harder if they can flip the Keystone state. Democratic Lieutenant Governor John Fetterman has consistently led the race, but Republican Celebrity Doctor Mehmet Oz has been slowly narrowing his lead over the last month.

I built a weighted demographic polling average for the Pennsylvania Senate race, and I'm using it to predict how undecided voters may break in the closing weeks of the campaign. As you've probably heard, polling averages are much more predictive than using one poll. That fundamental truth has been an important cornerstone of our election forecasts at RacetotheWH. Let's apply the same practice to crosstabs - giving more weight to high-quality pollsters that recently released polls.

Across over 10 polls, here are the number of undecided voters for each party in Pennsylvania:

Democrats: 7.6%
Republicans: 12.2%
Independents: 22.6%

How would the race look if we adjust the polling with this in mind? We will assume that the undecided will continue to break at the same rate by party. Our polling average shows they are breaking:

1. Democrats - Fetterman: 92.5% - Oz: 7.5%
2. Republicans - Fetterman: 9.1% - Oz: 92.5%
3. Independents - Fetterman: 53.2% - Oz: 46.8%

Next, we estimate the partisan makeup of the electorate. This is an imperfect science to put it lightly, but we'll use the same pollsters' estimate, by their weight in the average. Here's what we get:
Democrats: 41.3%
Republicans: 42.0%
Independents: 16.6%

Now, we've got some valuable information, and we can easily get a rough estimate of how many undecided voters there are by party.
Democrats: 3.1%
Republicans: 4.9%
Independents: 3.7%

We'd expect Fetterman and Oz to gain this many voters, again assuming voters continue to break the same way:

1. Dems: +2.88%
2. Reps: +0.45%
3. Ind: +1.95%
Total: +5.28% for Fetterman

Mehmet Oz:
1. Dems: +0.23%
2. Reps: +4.47%
3. Ind: +1.71%
Total: +6.41% for Oz

For the overall race, the sample of polls we're using shows John Fetterman leading Dr. Oz 48.0% to 42.0%, which gives him a 6% lead. Once we add the undecided voters, this is the new margin:

Fetterman: 51.9%
Oz: 48.1%
Lead: Fetterman +3.7%

Fetterman Campaign Ad - Labels

I think this provides some clear indication that Oz is likely to narrow the gap, but will continue to trail Fetterman unless the nature of the race changes. How can Oz overcome this? First, he could win if Republicans have a strong and decisive turnout advantage. Second, he could win a a higher percent of undecideds than the share of voters he’s currently winning by party.

There's no easy way to anticipate option 1 until after election day, so let's dig into the second option. The bad news for Oz - it's going to take a lot for him to make up ground. If Dr. Oz wins 80% of undecided independent voters, he'd still trail by 1.4%.  For Oz to take the lead, he'd need to do much better across the board, like winning 98% of Republican undecideds, 10% of Dem undecides, and 87% of Ind undecideds. That's no easy task

This provides some strong evidence that Oz will need to do more than just decisively win the undecided vote. He'll need to win a slice of the voters currently planning to support Fetterman. 

A few things could go wrong here. First, the polling cross tabs could be wrong. We are better positioned here than most because we are using 10 polls, and weighing by pollster accuracy. But cross tabs can still be unreliable. Second, even the top-line polling could be wrong again. If we have a historic 2020-style polling miss nationally, this race becomes hyper-competitive.

Mehmet Oz Campaign - Attack Ad Against Fetterman

The central takaway is that we can expect Oz to gain some ground on Fetterman as undecided Republicans break in his favor. However, Fetterman will most likely have a lead entering the election unless Oz is able to change the mind of some voters currently supporting Fetterman.

For more information, be sure to explore the full interactive Pennsylvania Senate race Forecast . If you like the Demographic polling average, we have released one for these races.


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