Denver — Colorado’s Democratic-controlled House on Sunday passed a bill that would ban the sale and transfer of semiautomatic firearms, a major step for the legislation after roughly the same bill was swiftly killed by Democrats last year.

The bill, which passed on a 35-27 vote, is now on its way to the Democratic-led state Senate. If it passes there, it could bring Colorado in line with 10 other states – including California, New York and Illinois – that have prohibitions on semiautomatic guns.

But even in a state plagued by some of the nation’s worst mass shootings, such legislation faces headwinds.

Colorado’s political history is purple, shifting blue only recently. The bill’s chances of success in the state Senate are lower than they were in the House, where Democrats have a 46-19 majority and a bigger far-left flank. Gov. Jared Polis, also a Democrat, has indicated his wariness over such a ban.

Last year, a similar bill died in committee, with some Democratic lawmakers citing concerns over the sweep of a ban and promises they made to their constituents to avoid government overreach affecting most gun owners’ rights.

Democrats last year passed and Polis signed into law four less-expansive gun control bills. Those included raising the age for buying any gun from 18 to 21; establishing a three-day waiting period between the purchase and receipt of a gun; strengthening the state’s red flag law; and rolling back some legal protections for the firearms industry, exposing it to lawsuits from the victims of gun violence.

Those laws were signed months after five people were killed at an LGBTQ+ nightclub in Colorado Springs last year. Soon, the state will mark the 25th anniversary of the 1999 Columbine High School shooting that killed 13 people. Other mass shootings in Colorado include 12 people killed in 2012 at an Aurora movie theater and 10 people killed in 2021 at a Boulder supermarket.

“This is the state where the modern era of the mass shooting began with Columbine,” Democratic Rep. Javier Mabrey said in urging fellow lawmakers to join other states that ban semiautomatic weapons.

Republicans decried the legislation as an onerous encroachment on the U.S. Constitution’s Second Amendment. They argued that mental illness and people who do not value life – not guns – are the issues that should be addressed. People with ill intent can use other weapons, such as knives, to harm others, they argued.

Democrats responded that semiautomatic weapons can cause much more damage in a short period of time.

“In Aurora, when the shooter walked in that theater and opened fire,” Mabrey said, “and in less than 90 seconds shot up a room full of people. That cannot be done with a knife, that can’t be done with a knife.”