Federal elections are all run by the individual states, so a state ID would be all you need.
If there is a federal law requiring proof of citizenship, as is currently being argued in Congress, a state ID would not be all you need since they are not proof of citizenship.
alt Hacker News
If there is a federal law requiring proof of citizenship, as is currently being argued in Congress, a state ID would not be all you need since they are not proof of citizenship.