"The House of Representatives shall be composed of members chosen every second year by the people of the several states, and the electors in each state shall have the qualifications requisite for electors of the most numerous branch of the state legislature."
BS arguments from the Voting Rights Act be damned.
It seems to me that elections are state-controlled. House races are district by district by popular vote, Senate races are state-wide, too, managed by each state's secretary of state.
Even presidential elections are not really for the candidates nationally, but for state electors to the Electoral College.
Therefore, where does the federal government think it has the power to regulate the proof of eligibility of elections that occur entirely within a single state?
They will probably argue equal protection, but all voters within a state are equally protected. Practices that differ between states don't have to be identical as a definition of equal protection, because each state already has different rules for absentee voting, early voting, voting devices, etc. So, the interstate equal protection argument already fails.
All voting for all federal offices are solely intra-state affairs, and therefore should be under the regulation of each state as it sees fit.
Also, remember that in 2013 SCOTUS threw out the parts of the Voting Rights Act that allowed Eric Holder to tamper with southern state voting. They may be in a mood to give more voting control back to the states.
-PJ