The first is one I've touted before.
Nationalize the 1965 Voting Rights Act. Including the "preclearance" part. In my legal layperson's mind, especially when combined with the 1964 "one man, one vote" ruling by the Supreme Court, it could also be used to attack gerrymandering more generally.
The Act established extensive federal oversight of elections administration, providing that states with a history of discriminatory voting practices (so-called "covered jurisdictions") could not implement any change affecting voting without first obtaining the approval of the Department of Justice, a process known as preclearance.And there's legal grounds for this. State laws clearly designed to impede the right to vote of the urban poor, especially those of color, are to be found in several Rust Belt states where the GOP has recently gained state control. Also, American Indians arguably face voting discriminations in far more counties and states in the western United States than is often reported.
Tool No. 2?
Employ the 14th Amendment. Specifically, the second sentence of Section 2:
But when the right to vote at any election for the choice of electors for President and Vice President of the United States, Representatives in Congress, the Executive and Judicial officers of a State, or the members of the Legislature thereof, is denied to any of the male inhabitants of such State, being twenty-one years of age, and citizens of the United States, or in any way abridged, except for participation in rebellion, or other crime, the basis of representation therein shall be reduced in the proportion which the number of such male citizens shall bear to the whole number of male citizens twenty-one years of age in such State.That's right. Arguably, it's Congress' power to enforce this, but, a strong President could take the bit in his mouth, and if necessary, sue Congress to take three House districts from Texas, two from Florida, or whatever else is deemed necessary. (Or one or two from Michigan, for that matter, per the discussion above.)
Of course, per the start of discussion, this administration would never do it.