Updated: October 31, 2013, 1:09 PM

This week was an important one for opponents of an Arizona election law designed to throw voters off the rolls and make it harder for third parties to get elected.

On Tuesday, Arizona Secretary of State Ken Bennett (R) certified that a referendum on the law, known as HB 2305, will be on the ballot in next year’s general election.

HB 2305 passed earlier this year. Considered a voter suppression effort by opponents, the law would raise the bar for third parties getting on the ballot, add obstacles to citizens initiative efforts, and kick voters off that state’s permanent early voting list if they fail to vote in two consecutive elections, among other things. The referendum effort began just days after the law was signed by Gov. Jan Brewer (R) in June.

“Today was a big win for Arizona voters and voting rights, but it’s only part of the battle,” Julie Erfle, chairwoman the umbrella group that backed the referendum effort, said in a statement on Tuesday. “The public response to our effort has been overwhelming across party lines, and we are absolutely confident that Arizona voters will toss these unnecessary and self-serving voting roadblocks in the dumpster where they belong.”

This is a separate issue to Arizona’s move toward two-tier voting that TPM reported on earlier this month.

The umbrella group, Protect Your Right to Vote Committee, announced this week that Bennett had confirmed 111,000 valid signatures had been gathered for the referendum. 86,405 was needed to qualify for the ballot.

Robbie Sherwood, a spokesperson for the referendum effort, touted how quickly the signatures had been gathered.

“We literally had 90 days in a brutal Arizona summer to get the signatures,” Sherwood told TPM on Wednesday. “And we burned like the first week and a half just trying to get organized. We didn’t start gathering signatures until July 1. And we still came in with like 146,000. And then our verification rate was 80 percent, which is, again, unheard of here.”

But the fight may not be over. Barrett Marson, a spokesman for two political committees that support the law, told Tucson Weekly that his groups will go to court to try to invalidate some of the signatures collected.

“There are thousands upon thousands of signatures that are likely to be invalid,” Marson said. “It’s early in the game yet.”

Sherwood said his group was expecting a legal challenge on “some sort of technicality.”

“We’re expecting that and prepared for that,” he said.

An aide to Arizona state Rep. Eddie Farnsworth (R), who sponsored HB 2305, told TPM that Farnsworth was unavailable to speak about the referendum effort.

Marson spoke with TPM on Thursday afternoon, and reiterated the points he made to Tuscon Weekly.

“It’s still early in the process,” Marson said. “There are thousands of signatures gathered by circulators who have questionable backgrounds and residency issues. Actually, let me change the word questionable to felonious.”

Marson said that, in Arizona, non-residents collecting signatures for a ballot effort must register with the secretary of state. He and his groups believe a number of people who gathered signatures for the HB 2305 effort are out-of-state residents who did not register.

“It is incumbent on us to prove that in court,” Marson said. “But we’ve identified certainly enough that if a court agreed, they would be dropped off the ballot.”