TUCSON, Ariz. — An historic vote in the Pima County Sheriff's Department Wednesday night. The largest deputies union took a largely symbolic vote of "no confidence" against Sheriff Mark Napier.

Now they'll be asking the sheriff to not run for a second term in 2020.

The Pima County Deputy Sheriff Association has been in a legal battle, over pay, with Mark Napier.

Read the full letter from the union on the vote

It's been a problem that has plagued the Pima County Sheriff's Department for more than a decade, leading to eroding morale and staffing shortages, issues that KGUN9 has investigated.

RELATED: PCSD Staffing Crisis: Unions says overtime is off the chart

Napier vowed, before he took office, to fix it. A year later, his efforts set off a legal fight -- an unprecedented challenge of authority and dissension in the ranks.

Union president Eric Cervantez says members strongly believe that Napier is not committed to his campaign promises. In an campaign email back in 2016 -- Napier told the union:

"My intention is to serve one term, and only if the sentiment is that I am doing a good job, one more. That's it."

This past year Napier has said in public that he's seeking two more terms.

"A vote of no confidence for the sheriff means that he doesn't have the skills or the abilities to lead the department into the future," said PCDSA Vice President Ricardo Garcia.

"It's been three years now, and we have evaluated the things that transpired since he's been running the department, and we've compared it to the promises that he made to the deputies. That's basically what the foundation of this vote of no confidence was. What has he done since he's become the sheriff?" Garcia said.

The union says the results of the vote will be presented to the Sheriff. While the vote does not require any official action from Napier, the union hopes the sheriff will keep his promise and not run in 2020.