Why are electors not legally required to vote for their party?

Electors are not legally required to vote for their party primarily because the framers of the Constitution wanted to ensure that electors could exercise independent judgment. This reflects a belief in the importance of electors as individuals capable of making informed decisions rather than being strictly beholden to party loyalty. The framers envisioned the Electoral College as a mechanism that could balance popular opinion with informed deliberation, allowing electors to potentially cast their votes based on the best interests of the nation rather than strictly adhering to the results of the popular vote in their states.

While the question references the unconstitutionality of requiring electors to vote in accordance with their party, the fundamental reason lies in the intention behind the establishment of the Electoral College, which aimed to safeguard the process from purely partisan influences. Thus, the design of the system inherently supports the idea that electors can exercise their judgment, aligning with the framers' vision of a deliberative process in selecting the president.