With the Electoral College set to meet next week, millions of Americans horrified by the prospect of a Donald J. Trump presidency have implored red-state electors to vote for Hillary Clinton or an establishment Republican. Millions of Americans supportive of Mr. Trump find these efforts galling. But both sides agree on what to call such electors: “faithless.”

This is a loaded label. Is it warranted? Do presidential electors have an obligation to ratify their state’s popular vote?

As a matter of state law, the answer is mixed. Just over half of the states have enacted measures that instruct electors to vote for their party’s designated candidate. The rest have not. And even in the states that tell their electors how to vote, the penalties for disobeying tend to be modest and to go unenforced.

As a matter of federal constitutional law, there is little basis for thinking that electors must side with their party’s candidate when that candidate carries the state. The Constitution says only that they “shall meet in their respective states and vote by ballot.” Some evidence suggests that the framers envisioned the independent judgment of electors as a check against populist passions. Alexander Hamilton, for instance, wrote that the Electoral College would allow the presidency to be decided “by men most capable of analyzing the qualities adapted to the station, and acting under circumstances favorable to deliberation.”