Sending mail to or cold calling voters, okay, that should by all definitions be covered by the First Amendment. Verifying voter rolls, okay, reasonable.

But there is no justification for providing voter roll data to the wide public in a way that is machine readable. Or to provide these data to third parties (including political parties, candidates or PACs).

Candidates and parties can use USPS Bulk Mail, they do not need to know the names of potential voters to exercise their right to free speech. People interested to check if they or someone they know are on the voter rolls (or not, in the case of suspected/possible fraud) can do so in person or by mail.

The public policy purpose is to allow independent verification of who voted, in furtherance of trust in elections. It is arguably one of the reasons voter fraud is extremely rare in U.S. elections. “Many eyes make bugs shallow,” to steal a phrase.

Unfortunately, a lot of people still believe in widespread voter fraud despite the obvious and well-documented rarity.

I would say something similar about the availability of voter files, though. A lot of people are horrified they are available despite the obvious and well-documented lack of evidence it causes any significant harm.

I think this is a distinction without a real difference. There are a lot of candidates. Note that the voter file isn't simply a mailing list (it's also used for targeting events and messaging) and that under current jurisprudence the state can't create a blanket opt-out for citizens as you suggest it could.

> cold calling voters

That should be a capital offense if done for political purposes, commercial purposes or any other purposes that are not an emergency :)

> But there is no justification for providing voter roll data to the wide public in a way that is machine readable.

Why not? It's considered public information, just like political donation records.