A state may not advantage its citizens as against citizens of other states as a general rule. For example, it cannot give its citizens greater access to public forums for assembly.
The Constitution gives citizens in small states more electors per voter than citizens in large states. But is it right for a state to exacerbate that extra power by adopting a winner-take-all rule for choosing electors? Such a rule enables voters composing a mere plurality to name all the states’ electors in the Electoral College.
The right to assemble includes the right to move to a state that upholds and supports the political and policy preferences of any citizen. For example, a citizen may choose to live with others who are willing to pay higher taxes in return for more funding for public schools, public transportation, or other public benefits. However, by not granting citizens the right to vote with equal weight for president, a state inhibits the right to assemble with like-minded people in a community.
To illustrate, in 2016, under the current system, a citizen who prefers Trump over Clinton lost weight in voting by moving from Texas to California, or a Clinton-preferring citizen lost weight in voting by moving from California to Texas. This loss of equal weight is not a result of any operation of the Constitution’s Electoral College system: it occurs because states adopt a winner-take-all-rule instead of pledging their electors to choose the winner of the national popular vote or, as second order solution, allocating their electors proportionally like Nebraska and Maine.