Why is it so hard to know how many independent voters there are?

(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.)

Thom Reilly, Arizona State University

(THE CONVERSATION) Modern U.S. politics has largely been viewed through the lens of a two-party power structure: Democrats and Republicans. However, this may be changing. Increasingly, the media, pollsters, pundits and campaigns themselves are focusing on independent voters, saying they will be crucial to the outcome of the 2024 presidential election.

But even among political experts, there remains a good deal of disagreement on how many of these voters are out there. It’s possible that some voters identify as independent but really just have weaker political preferences than party die-hards, while still maintaining some loyalty to one party or the other. And some independent voters change their political identification from one cycle to another. That makes it hard to tell who an independent voter is and how many of them exist.

Most of what political researchers like me know about independents comes from survey data.

Though it might seem simple to look at state records of voter...