Twice since 2000 — with George W. Bush and then Donald Trump — Republicans have lost the national popular vote but won the Electoral College. That has left many Democrats furious with the system.

Eliminating the Electoral College would require a constitutional amendment, a highly unlikely prospect in a polarized nation. But after Tuesday’s midterm elections, Democrats will soon have enough power in statehouses across the country to try to circumvent it without an amendment.

Since 2007, 18 Democratic-run states and the District of Columbia have joined a legal framework that would pledge their Electoral College votes to the nationwide popular vote winner, rather than the winner in their state. The effect of the pact, if enacted and enforced, would be the same as replacing the Electoral College with the popular vote. The pledge would activate only if the states in the pact accounted for at least 270 electoral votes, the majority needed to win.

The states already in the pact represent 222 electoral votes.…