Your last primary is a good guess at your party, until it isn’t

In states without party registration, such as Ohio and Texas, a common way to give early voters a party is to use the party of the last primary they voted in. We tested that shortcut in North Carolina, where the true registered party is on file. Across 1,096,068 accepted early ballots as of Oct 22, 2026, the shortcut put the Democratic margin at D+21.2 against a true D+20.5. But it put 24% of early voters in Other, against a true 34%.

What it means

For the margin, the shortcut works. Using every primary since 2017, it lands within 0.7 points of the true D−R gap. That is why we use it in Ohio and Texas, where no registration exists, and why we report the margin from it with some confidence.

For the shares, it does not. The proxy gives D 48.4, R 27.2, Other 24.4. The true registration split is D 43.0, R 22.5, Other 34.4. Both parties look larger than they are and the unaffiliated group looks smaller.

Two errors cause this, and they pull in opposite directions:

• Unaffiliated voters who vote in primaries get a party. Of 377,501 unaffiliated early voters, 160,307 last took a Democratic primary ballot and 102,289 a Republican one. The proxy counts all 262,596 as partisans.
• Partisans who skip primaries become Other. 101,759 registered Democrats and 50,582 registered Republicans have no primary on record since 2017. That is about 21% of registered partisans, and the proxy puts them all in Other.

The two errors almost cancel on the margin. They do not cancel on the size of each group.

What it doesn’t mean

It does not mean the shortcut works everywhere. North Carolina has party registration and lets us check; Ohio and Texas do not. Primary turnout patterns differ by state, and a contested primary on one side can tilt the proxy for a whole cycle.

The time window matters. Using only primaries since 2022, the proxy gives D+16.0. Using only primaries since 2024, D+15.3. Using only the 2026 primary, D+17.4, with almost half of early voters (49.2%) in Other. The more history the proxy can see, the closer it gets, and the full-history version is the only one within a point of the truth.

It does not tell you how anyone voted. Registration is not vote choice, and neither is a primary ballot. An unaffiliated voter who took a Democratic primary ballot may have done so because that primary was the more competitive one.

How we checked

We used the North Carolina State Board of Elections absentee file for the Nov 3, 2026 general, keeping accepted ballots only: 1,050,226 cast early in person and 45,846 by mail. Each record carries the voter’s registered party.

We joined it on voter ID to the statewide voter history file dated Oct 18, 2026, which lists every primary each voter took part in, with the party ballot chosen. For each early voter we took the most recent Democratic or Republican primary ballot within the window and called that the voter’s proxy party. Voters with no such ballot were Other.

We then compared the proxy with registration for every voter and counted where each registered group landed. No voter-level data was kept; only the counts above were stored.