A Colorado bill that could help change how the country elects the president is heading to its final vote after passing out of a House committee on a party-line vote Tuesday night.

The bill would add Colorado to an agreement between a growing number of states to award their Electoral College votes to whomever wins the national popular vote for president. It passed the Senate in January without a single Republican voting for it, and now heads to the House where Democrats hold a substantial majority.

The debate over the bill went well into the night Tuesday, and much of it centered around whether it’s constitutional for states to band together and fundamentally alter presidential elections. And while only a few the more than 80 people who testified mentioned President Donald Trump mentioned by name, the results of 2016 election (where Trump lost the popular vote) worked their way into the testimonies of people on both sides of the issue.

Jenna Ellis, a constitutional law attorney who works for Colorado Family Action, gave the committee three reasons why she thinks the bill is unconstitutional.

The first was that it would violate a part of the U.S. Constitution called the compact clause, which says states can’t enter into agreements with each other without federal approval. Second, the bill would remake the Electoral College without a constitutional amendment. And third, it could impact the part of the 12th Amendment that gives Congress the power to decide the presidency if no candidate gets the 270 votes required to win the Electoral College.

Eleven states and the District of Columbia have joined the national popular vote interstate compact so far, bringing with them 172 electoral votes. Rep. Jovan Melton, D-Aurora, asked Ellis why no one has brought a legal challenge against those states.

Ellis responded with a question of her own, asking Melton whether he thought fetal heartbeat bills were constitutional in the states where they haven’t faced a court challenge.

Rep. Jeni Arndt, D-Fort Collins, disagreed with Ellis about whether her bill violates the compact clause. She pointed to several Supreme Court decisions where the court let states enter into certain agreements. She also said the U.S. Constitution gives states plenary or absolute power to decide how they award their electors.

“I believe in this bill. I believe it enfranchises every single American,” Arndt said.

Secretary of State Jena Griswold’s office sent a representative from her office to testify in support of the bill, saying it wouldn’t change how Colorado runs its elections.

But Save Our States director Trent England saw one major logistical problem for secretaries of state: The federal government doesn’t certify a national popular vote total.

Senate Bill 19-042 directs the chief election official of each member state to determine the number of votes cast for each candidate in all 50 states and the District of Columbia and then add all of those together themselves.

“You’re asking for 51 different certifications,” England said.

That, in his opinion, could get messy fast — especially because vote counting often goes on for days and even weeks after an election. And it’s possible states would come up with different numbers for the national popular vote total.

“Presidential candidates don’t even bother campaigning in 38 states,” Stan Gelb of Longmont said. “This makes many potential voters cynical and/or apathetic resulting in many not voting at all.”

He said he thinks that’s one reason America’s voter turnout is lower than other nations. Gelb didn’t mention President Trump by name, but he told the committee that voter apathy leads to being ruled by “evil men.”

Greg Trouth of Bailey also touched on the 2016 election, saying the Electoral College “performed exactly as it was intended. It gave a voice to the lesser populated states to withstand the large populated states and avoided a potentially tragic election.”

Rep. Dave Williams, R-Colorado Springs, tried unsuccessfully to add an amendment that would refer this decision to Colorado voters. The national popular vote bill now heads to the House floor for a vote.