In the wake of the 2016 election, when Democrats lost the presidential election but won the popular vote for the second time in 20 years, it’s easy to understand why momentum to abolish the Electoral College once again gathered on the left. It’s not so easy to understand, though, why Republicans have become so committed against the idea of a national popular vote in response.

The Denver Post recently reported that Republican Sen. Cory Gardner actually donated $50,000 to an effort to withdraw Colorado via a referendum from the National Popular Vote Interstate Compact. The compact is an agreement that state legislatures have voted to join that would pool the electoral votes from among the participating states. Once the 270-vote threshold has been reached between those participating states, they would award all of those votes to whoever wins the popular vote across all 50 states and the District of Columbia. Fifteen reliably blue states, plus the District of Columbia, have joined the compact since 2006, but it has not been as popular among Republicans—perhaps because of some kind of partisan loyalty to the Electoral College.