Article I section 4:
The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.
So it is the states, except to the extent that Congress (not the president!) gets involved.
Even in Federal elections? I thought I read somewhere that rules for Federal elections are made by the Federal gov.
Article I section 4: The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.
So it is the states, except to the extent that Congress (not the president!) gets involved.