And not just any lawmaker. Colorado State Sen. Tom Sullivan is one of the five members of the Senate State, Veterans and Military Affairs Committee, which is comprised of three Democrats and two Republicans. That's the committee that will be hearing the gun ban bill approved by the House last week, and Sullivan could cast the deciding vote on the legislation.

Sullivan, whose son Alex was murdered in the Aurora movie theater shooting in 2012, has championed the gun control bills that have been signed into law in Colorado over the past decade, and has spoken in favor of a national "assault weapons" ban. But he's also been skeptical of a state-level ban for some time. Last year he opposed including a similar ban in a gun control package, warning it would be both bad policy and bad politics.

Federal, absolutely, he responded. State? No: It would inflame gun-rights supporters, was unlikely to be enforced and would not curb the vast majority of shootings.

“Banning? That doesn’t end well for us,” Sullivan said later that morning in his office. “And I’m speaking as the father of a son who was murdered by an assault weapon.”

With their biggest majority in 60 years, Colorado Democrats returned to the Capitol in January vowing to take on gun violence in a state scarred by mass killings — Columbine, the Aurora theater, the Boulder supermarket, Club Q. On April 28, activists and lawmakers celebrated as Gov. Jared Polis (D) signed four gun-control bills some hailed as the most significant ever. 

But missing was a proposal that divided gun-control proponents and highlighted the evolving political landscape of a blue state with a deep Western hunting and agricultural ethos: A ban on the sale or transfer of assault weapons had been defeated a week prior in a House committee on which Democrats hold nine of 13 seats. The view of Sullivan, one of the legislature's leading gun-control champions, helps explain why. 

“This isn’t transportation. This isn’t education. This is guns. We haven’t been comfortable talking about guns in the state of Colorado — ever,” Sullivan said. “Why don’t we try to strategically move forward, instead of blowing up the house?”

Has anything changed since last year? Sullivan isn't saying how he'll vote when the bill comes up in committee, which is a statement of its own, I suppose. 

He worries the policy would spur a rush to buy the newly banned firearms, inadvertently increasing the number in circulation while not addressing the leading causes of gun violence. Other policies, he has argued, would do more to stem the tide. 

Sullivan did not commit to a firm yes or no vote on Thursday. He reiterated his past skepticism and said he would be “crystal clear with everybody where I am” when the committee voted.

“If I had thought (an assault weapons ban) was the way to go, I would have done it the day after Alex was murdered with one,” Sullivan said.

If any Democrat in the Senate could vote down a gun ban bill without immediately drawing a well-funded primary opponent, it's Sullivan. Moms Demand Action and Everytown can't credibly accuse him of being a "tool of the gun lobby" or an NRA lapdog. They've endorsed every one of his campaigns, and he's been a staunch ally since he was elected to the Senate. And it's not like he's opposed to bans on semi-automatic rifles in general. He just thinks a federal ban is necessary, rather than a hodge-podge of state-level bans in a handful of blue states. 

The Senate committee isn't expected to take up the House bill until early May, and Sullivan will be the subject of intense lobbying between now and then, both from his colleagues and gun control groups. Still, he's not the only Senate Democrat that gun controllers have to worry about. Senate President Steve Fenberg told the Denver Post he's aware of "several no votes", and Democrats can only afford to lose five of their members if the bill reaches the Senate floor. 

Gov. Jared Polis's press secretary has also publicly stated that the governor is "skeptical" of the proposal, so passage is far from assured even if Sullivan reverses course and votes to advance the bill out of committee. I'm sure his anti-gun colleagues will be encouraging him to send a message by supporting the bill, but he was right when he said last year that passing the bill would inflame Second Amendment supporters and would lead to a surge in sales before the ban takes effect. Like the other gun control bills that have been enshrined into law in the state over the past decade, banning so-called assault weapons would do nothing to make Colorado any safer. I don't agree with Sullivan's position that a federal ban would be better, but he's not wrong about the problems of a state-level "assault weapons" ban.