Democrats’ victories in key battleground states have opened a path to a fundamental change in presidential elections, but pursuing it could diminish those states’ influence in the 2028 race.

With unified control of state government in Pennsylvania, Michigan, Wisconsin, Arizona and Nevada beginning next year, Democrats face pressure to join the National Popular Vote Interstate Compact. Members agree to award their electoral votes to the national popular vote winner, rather than the winner in their own state, once states totaling at least 270 electoral votes have joined.

Eighteen states and Washington, D.C., representing 222 electoral votes, have enacted the agreement. Adding Pennsylvania, Michigan and Wisconsin, plus either Arizona or Nevada, would put the compact over the threshold.

Leaders in the newly Democratic-controlled states have expressed support for a national popular vote, but it remains uncertain whether they will prioritize the compact after campaigns focused on lowering costs.

Incoming Arizona Senate Majority Leader Priya Sundareshan said her caucus would take up the issue, though the timing is unsettled. She said she had not discussed it with Gov. Katie Hobbs, whose office declined to comment.

Pennsylvania Gov. Josh Shapiro told POLITICO he was “open” to signing his state into the compact. He also said at Crooked Media’s Crooked Con that the national popular vote “makes sense” and pledged to work with lawmakers on a mechanism.

Incoming Michigan Senate Majority Leader Darrin Camilleri said he was open to the change but expected Republican lawsuits. Michigan could be a “tipping-point” state, he said, making it important that “everybody is on the same page.”

Wisconsin Gov.-elect David Crowley backed a bill to join the compact in 2019. Asked about his plans as governor, he said he was focused on assembling a transition team.

Nevada Democrats passed a compact bill in 2019, but then-Gov. Steve Sisolak vetoed it, citing concerns about the influence of smaller states. Gov.-elect Aaron Ford’s office declined to comment.

Despite the uncertainties, advocates are optimistic about reaching the threshold before 2028. “I’ve never been more confident in my life,” said Patrick Rosenstiel, a spokesperson for the bipartisan National Popular Vote group.