That's partly because Colorado has changed, as Taylor put it, "from the old, rugged West" to a "kind of mini-California" in the last 15 years. Jill Hanauer, the president of the Denver-based political consulting firm Project New America, said Colorado is more urbanized and diverse today than it was a decade and a half ago.

"The demographics are such that you have a young state, a state that has experienced rapid growth," Hanauer said. A growing Latino population, "while they are gun owners, they support gun safety measures," she said.

"The combination of shifting demographics that have taken place in Colorado, the tragedies that we've seen and pragmatic leadership all makes it possible to pass these laws that probably could not have been even considered 10 years ago."

Colorado voted to make background checks for gun-show purchases mandatory after Columbine, when investigators learned that the weapons used by the teenage killers were bought by an 18-year-old at a gun show to avoid a background check. The buyer, Robyn Anderson, later told a state House of Representatives committee that the gun purchases had been "too easy."

Many other state legislatures are debating gun laws in the wake of the Newtown killings, but not all of them are aimed at restricting guns.

Many of the more than 1,000 bills pending around the country would nullify the effect of any federal ban on firearms, assault weapons and high-capacity ammunition magazines, according to the National Conference of State Legislatures.

And nationwide, a CNN/ORC International poll out Monday suggested that support for major restrictions on guns may be fading three months after the Newtown killings. While a majority of Americans favored major restrictions on guns or an outright ban in the immediate aftermath of that massacre, support for gun control has fallen to 43% since that December tragedy, the poll found.