Farmington, New Mexico (CNN) A year after 3 million gallons of heavy metal sludge from the shuttered Gold King Mine gushed into a tributary of the Animas River, the Navajo Nation is suing the Environmental Protection Agency for what it sees as negligence in cleaning up the disaster -- serving up a potent election-year issue for Republicans against one of their favorite targets.

The EPA has taken responsibility for the accidental release of toxic acid mine waste -- including lead and arsenic -- that turned the Animas River an unsightly shade of orange last August. But in the lawsuit filed Tuesday, the Navajo Nation alleges that the EPA has failed to properly remediate the disaster and compensate the thousands of farmers who rely on the San Juan River, which flows from the Animas through New Mexico and Utah, to irrigate their crops and sustain their cattle and sheep.

Touching the livelihood of voters in four western states -- Arizona, Colorado, New Mexico and Utah -- the spill could serve as a symbol of government incompetence for Republicans, who have long railed against what they view as the overreach and overregulation of the EPA, especially under President Barack Obama.

It is also a reminder of how vacuous the policy debates have been over the role of government in the 2016 presidential race, as most of the attention has focused on Donald Trump's temperament and gaffes, along with Hillary Clinton's trustworthiness and her email scandal.

EPA press secretary Melissa Harrison told CNN Tuesday that it cannot comment on pending litigation. Overall, the EPA has said it has dedicated more than $29 million to the response to the incident across the states and tribal areas, money that is intended to mitigate "ongoing acid mine drainage from the Gold King Mine," while also covering water quality sampling, field evaluations and personnel.

For Republican lawmakers struggling to hold their seats as Trump's poll numbers plummet, the incident is exactly the kind of local issue that GOP strategists believe incumbents in the Mountain West should focus on to draw the spotlight away from the flailing Republican nominee.

In Arizona, Native Americans form a crucial voting bloc that typically trends toward Democrats. But distrust of the EPA in the wake of the spill has the potential to alter those political dynamics.

Republican John McCain, who will likely face a difficult challenge for his Senate seat from Democrat Ann Kirkpatrick after Arizona's August 30 primary, has aggressively criticized the EPA's handling of the Gold King Mine spill -- going so far as to call for a criminal investigation. Earlier this month, the Office of the Inspector General initiated a criminal investigation into the Gold King Mine incident.

Kirkpatrick, whose congressional district includes part of the Navajo Nation, has also expressed outrage at the EPA's response, particularly the slow process to compensate farmers who lost crops because they were afraid to irrigate them with water from the river. Citing the fears among the Navajo people that the river water is still not safe, Kirkpatrick said at one point that she was appalled that babies living on tribal land may "be drinking contaminated formula."

Recent EPA reports say that surface water both in Colorado and in the San Juan River in New Mexico have returned to "pre-event conditions" and that the water is safe for recreation. The agency's water quality experts have also deemed the San Juan River safe for agriculture and irrigation.

But many Navajo are worried about potential long-term health effects from the heavy metals that have settled into the river sediment upstream from the Navajo Nation. Snowmelt and heavy rains can dredge up that sediment and send it coursing downstream once again.

The lawsuit

In the lawsuit filed Tuesday morning, which is not seeking a specific dollar amount in damages, the Navajos allege that the EPA has failed to adequately remediate the disaster a year after the dispersal of 880,000 pounds of heavy metals into the Animus river watershed near Silverton, Colorado. The chemicals flowed from the Animas, along some 200 miles of the San Juan River in New Mexico, which runs through the Navajo Nation and continues into Utah.

"After one of the most significant environmental catastrophes in history, the Nation and the Navajo people have yet to have their waterways cleaned, their losses compensated, their health protected or their way of life restored," the complaint filed by the Navajo Nation in US District Court for the district of New Mexico alleges.

"Despite repeatedly conceding responsibility for the action that caused millions of dollars of harm to the Nation and the Navajo people, the U.S. EPA has yet to provide any meaningful recovery. Efforts to be made whole over the past year have been met with resistance, delays, and second-guessing. Unfortunately this is consistent with a long history of neglect and disregard for the well being of the Navajo," the lawsuit says.

The Navajo Nation is being represented by John Hueston, who was the lead prosecutor in the Enron trial against Ken Lay and Jeff Skilling.

The lawsuit alleges that the EPA, its contractors and the mining companies, who are also named in the lawsuit, ignored the buildup of contaminants over many years, failed to follow "reasonable and necessary precautions" to avoid the spill when they began the mine cleanup operation in August 2015.

"The river has always been a source of life, of purification, and of healing," said Ethel Branch, the Attorney General of the Navajo Nation, who noted that the Navajo people harvest minerals from the banks of the river for use in their religious ceremonies. "Now it's been transformed into something that's a threat. It's been pretty traumatic in changing the role of the river in the lives of the people who rely on it."

In the immediate aftermath of the Gold King Mine spill, one water sample showed that the level of lead in the Animas River was 12,000 times higher than normal. The river was also contaminated with high levels of arsenic, beryllium, cadmium and mercury.

Branch said the spill has created a stigma of fear around the organic and heirloom crops grown by the Navajo in the San Juan watershed. The health concerns have made it more difficult for Navajo farmers to sell their produce, she said.

"We're not going to know the health impacts of the exposure to the water for five to 10 years -- maybe more," Branch said. "And it's not just direct exposure, the community is also concerned about eating food that's been watered with contaminated water, or eating livestock that has consumed the water."

Distrust of the EPA was amplified by the fact that Navajo officials say they were not notified of the release of the toxic sludge upstream until nearly two days after the spill. Branch noted that some of the water delivered in tanks by the EPA for irrigation had an oily sheen or was discolored. The agency said it tested the water in the tanks and that it met "all applicable EPA standards for drinking water.

Though they deem the water to be safe, the EPA's website on the Gold King Mine spill warns people near the affected waterways to "avoid discolored sediment" and suggests that children under the age of six should be supervised when playing around the river "to ensure they don't ingest river water or sediment."

Agency officials have pointed out that the Gold King Mine spill is part of a much larger problem of contamination stemming from more than 160,000 mines in 12 western states.

But Branch sees that debate as a distraction from the ongoing issues affecting her community.

"From the very beginning, the EPA tried to shift the conversation to the overwhelming nature of dealing with abandoned hard rock mines in the West, in my view to dilute the significance of what occurred and the need for them to be accountable and to clean up the contamination or address it in some way."