The switch could cost state and local governments around $5 million in presidential election years.
Critics of the measure argue it’s being rushed through the process at the end of the legislative session, with little time for public input.
"If this is truly about giving the people a voice, I have to ask, why now?" said Rep. Patrick Neville, R-Castle Rock.
Bill sponsor Dominick Moreno, D-Commerce City, said the measure is a response to public demand.
"Because folks are angry about how the Colorado caucuses were conducted this last cycle," Moreno said. "If we want to show them that we heard them, then we should do something this session."
Some Democratic voters weren’t able to participate at their over-crowded caucus locations this year. Many Republicans have complained about their party not holding a straw poll.
The Associated Press contributed to this report.