Proposition 308, the measure that would open in-state tuition to undocumented high school graduates in Arizona, passed by a tight margin Monday night, "yes" outpaced "no" by about 60,000 votes, according to the Associated Press.

Approval for the measure had held a slim but steady lead in the days leading up to the official call Monday.

Tyler Montague, a Republican and the chair of the Yes on 308 campaign, said the initiative arrived on the ballot after years of work from grassroots groups.

"I’m unbelievably happy about this, the people that were there and made sacrifices for us, many of these legislators who supported us were viciously attacked in their campaigns," he said during a virtual press conference about the status of the measure on Monday.

ASU student Angel Palazuelos talks with Show host Mark Brodie about what Prop. 308 means

Montague was joined by Phoenix business leaders and other groups supporting Proposition 308, including LUCHA, Chicanos Por La Causa and the American Business Immigration Coalition.

Passing Proposition 308 overturns a portion of a measure passed in 2006 barring undocumented residents from accessing a host of public services.

The measure gained notable GOP support in the weeks leading up to the election. Advocates say after polling, expected to get around 22-25% of the Republican vote.

More stories from KJZZ

• Arizona midterm election results
• Arizona propositions results