DENVER — With politicians in Washington deeply divided over new gun regulations, an urgent national debate ignited by the massacre at Sandy Hook Elementary School is storming into state legislatures across the country. And nowhere is that debate more emotionally charged or politically consequential than here in Colorado, a reluctant crucible for the battle over guns.

This state, one of hunters and sport shooters, has endured two of the most horrific mass shootings in American history, and this year for the first time in more than a decade it could pass major gun-control legislation.

Gun-control advocates say it is a moment forged in part by the massacre inside a suburban Denver movie theater in July that left 12 people dead and dozens wounded. But it is also one created by demographics, of population shifts that have nudged the political center left while transforming traditionally rural, conservative swaths of the West.

“We’ve had it with mass shootings,” said Beth McCann, a Democratic state representative. “People just don’t want to hear about another massacre. This is enough.”