The US constitution amendment 26 says US citizens have the right to vote in elections:

1. The right of citizens of the United States, who are eighteen years of age or older, to vote shall not be denied or abridged by the United States or by any State on account of age.

2. The Congress shall have power to enforce this article by appropriate legislation.

The implication here is that some evidence of US citizenship is required to vote.

The average semi-literate democrat voter should have enough brain power to drag his-her-its entitlement-seeking arseface to the county records bureau to retrieve their own birth certificate.

A birth certificate indicating birth inside the US is sufficient to prove US citizenship.