Colorado lawmakers are trying to change the open primary law voters passed in November before it goes into effect.

Supporters say SB17-205 fixes problems that would make Colorado’s first primary in 2018 messy and confusing.

But opponents claim the changes would strip Proposition 108 of its intent.

Proposition 108 passed in the November 2016 election and gave voters who don’t belong to a political party the right to vote in any party’s primary.

The ballot initiative directed county clerks to send one, big ballot with all the primaries to unaffiliated voters with instructions to pick only one party’s primary.

The bill working its way through the statehouse would change those rules. Unaffiliated voters would get a ballot for each party’s primary with instructions to mail the one they used back. And it would create a public record of which primary ballot that person returned.

“Being an unaffiliated shouldn’t shield you from that election procedure,” Sen. Kevin Lundberg (R-Larmier County) said. “Ever other participation in an election has always been a public record.”

Lundberg is one of the bill’s sponsors. He pointed out that just because the Secretary of State’s Office has a record of you voting in the Republican primary, that doesn’t mean you’re a Republican.

“In my mind, I can’t predict that,” Lundberg said. “You either want to get the very best person selected in one party, or maybe you want to get the worst person selected in an opposing party.”

Exactly who you voted for would always remain private.

But the backers of Proposition 108 don’t see it that way.

“It’s disappointing when you work hard for something for five years and you get it passed with overwhelming support, and then lawmakers try to subvert the intent of the voters,” said John Hereford, who helped spearhead the ballot initiative. “It’s frustrating.”

Hereford admitted the bill was better when it passed the state Senate Monday than it was when it was introduced earlier this month.

The first version would have marked an unaffiliated voter with a defacto party registration based on the primary ballot he or she chose.

“Then, they would automatically send you the Republican ballot in perpetuity … ,” Hereford said. “That undermined the [law’s] clear intent.”

That’s why the Let Colorado Vote campaign launched an ad against Lundberg and his co-sponsor Sen. Steve Fenberg (D-Boulder).

The ad tells viewers that party bosses are pressuring lawmakers to overturn their vote to open the primary process in Colorado.

“It’s a dirty trick pushed literally in the dark of night,” the ad’s narrator says. “That will add unnecessary barriers to voter participation, threaten ballot privacy and violates the very ballot measure voters just approved.”

The group pulled the after lawmakers removed the part that allowed county clerks to use an unaffiliated voter’s primary voting record as a defacto party registration.

“We’re neutral on the bill now,” Hereford said. “It’s going to be public knowledge, and we’re not crazy about that … But that’s a fight for another day.”