Jon Austria, AAssociated Press
Carolyn Yazzie fills in her ballot, Tuesday, July 21, 2015, at the Shiprock Chapter House in Shiprock, N.M., during the Navajo Nation's referendum election to decide the language qualifications for future leaders.

FLAGSTAFF, Ariz. — Navajos are voting Tuesday in a rare referendum that could loosen the requirement that presidential hopefuls speak the tribe's language, a mandate that became a central issue during the last election and led to court challenges that delayed it for months.

Tribal law requires that candidates for president and vice president understand Navajo and speak it fluently, which can be enforced by tribal courts.

A simple majority of "yes" votes in Tuesday's election means Navajos will determine if candidates speak and understand the language well enough to hold office, starting with the 2018 election. A "no" vote leaves the current requirement in place.

The question of what it means to be fluent in Navajo overshadowed the most recent Navajo presidential election that was delayed for months by court challenges. The tribe's Supreme Court said the requirement was reasonable and ordered a lower court to determine if candidate Chris Deschene met the qualification after he was challenged by opponents in the primary election. Deschene refused to be tested on his language skills and was replaced on the ballot.

More than 122,000 Navajos are registered to vote in Tuesday's election. About a handful of referendum elections have been held on the reservation, including one that rejected a tribal takeover of federal health care services and three on tribal casinos. The only citizen-led ballot measures resulted in the reduction of the Navajo Nation Council from 88 members to 24 members and a presidential line-item veto.

Tribal lawmakers gave time to people from opposing sides of the language debate to address people in the council chambers Monday during the opening day of their summer session. Many have rallied around Deschene and said that Navajos who are encouraged to leave the reservation to get an education and return to help their people shouldn't be faulted for not knowing the language.

Others say not having a president speak fluent Navajo diminishes the value of the language said to be handed down by deities and that goes hand-in-hand with culture and tradition.