[Bob]

It could also be viewed as a reasonable restriction for a specific place (the polling location), at a specific time (during voting), with a specific purpose (to prevent electioneering). Many, if not most, states have similar laws regarding political expression at polling places during voting hours.

[William Tell]

"It could also be viewed as a reasonable restriction ..."

I think you omitted the expectation that the restrictions must be "content neutral".

The conversation I quoted above is all the proof that one would need to see that the practice of censoring voters is not content neutral.

[Buckeye McFrog]

Many, if not most, states have similar laws regarding political expression at polling places during voting hours.

Does not mean they are Constitutional. I have a feeling if someone wearing a Black Lives Matter t-shirt to the polls was prosecuted the courts would find a way to toss those laws faster than you can say "RAAAAAAAACIST!"