such Manner as the Legislature thereof may direct.” This Court has
described that clause as “conveying the broadest power of determination” over who becomes an elector. McPherson v. Blacker, 146 U. S. 1,
27. And the power to appoint an elector (in any manner) includes
power to condition his appointment, absent some other constitutional
constraint. A State can require, for example, that an elector live in the
State or qualify as a regular voter during the relevant time period. Or
more substantively, a State can insist (as Ray allowed) that the elector
pledge to cast his Electoral College ballot for his party’s presidential
nominee, thus tracking the State’s popular vote. Or—so long as nothing else in the Constitution poses an obstacle—a State can add an associated condition of appointment: It can demand that the elector actually live up to his pledge, on pain of penalty. Which is to say that
the State’s appointment power, barring some outside constraint, enables the enforcement of a pledge like Washington’s.
Nothing in the Constitution expressly prohibits States from taking
away presidential electors’ voting discretion as Washington does. Article II includes only the instruction to each State to appoint electors,
and the Twelfth Amendment only sets out the electors’ voting procedures. And while two contemporaneous State Constitutions incorporated language calling for the exercise of elector discretion, no language of that kind made it into the Federal Constitution. Contrary to
the Electors’ argument, Article II’s use of the term “electors” and the
Twelfth Amendment’s requirement that the electors “vote,” and that
they do so “by ballot,” do not establish that electors must have discretion. The Electors and their amici object that the Framers using those
words expected the Electors’ votes to reflect their own judgments. But
even assuming that outlook was widely shared, it would not be enough.
Whether by choice or accident, the Framers did not reduce their
thoughts about electors’ discretion to the printed page. Pp. 8–13.
(b) “Long settled and established practice” may have “great weight
in a proper interpretation of constitutional provisions.” The Pocket
Veto Case, 279 U. S. 655, 689. The Electors make an appeal to that
kind of practice in asserting their right to independence, but “our
whole experience as a Nation” points in the opposite direction. NLRB
v. Noel Canning, 573 U. S. 513, 557. From the first elections under the
Constitution, States sent electors to the College to vote for pre-selected
candidates, rather than to use their own judgment. The electors rapidly settled into that non-discretionary role. See Ray, 343 U. S., at
228–229. Ratified at the start of the 19th century, the Twelfth Amendment both acknowledged and facilitated the Electoral College’s emergence as a mechanism not for deliberation but for party-line voting.
Courts and commentators throughout that century recognized the
presidential electors as merely acting on other people’s preferences.

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