* This story has been updated to include a comment from Sanders' campaign.

In the late 1990s, when now-U.S. Sen. Bernie Sanders of Vermont was a member of the House, he supported a compact between Maine, Vermont and Texas that originally proposed dumping low-level radioactive waste in a small minority community in far-West Texas, putting him at odds with other progressive congressmen.

Though the waste never made it to Sierra Blanca, a low-income, largely Hispanic town in Hudspeth County, Sanders’ efforts have attracted renewed attention online in the lead-up to Tuesday's Texas primary. Critics suggest that the candidate’s role in promoting the compact — which ultimately brought the waste to a different site in West Texas — undermines his otherwise progressive record.

“It reflects very poorly on him,” said longtime environmental justice activist Dr. Robert Bullard, dean of the Barbara Jordan-Mickey Leland School of Public Affairs at Texas Southern University and the author of Dumping in Dixie. “Shoving this down people’s throats is not progressive politics. It was business as usual. It’s a classic case of rich people from a white state shifting something they don’t want to a poor minority community somewhere else.”

But other activists in the area have forgiven Sanders for his role in the proposal. Bill Addington lives in Sierra Blanca and was a leading activist against the nuclear waste compact, creating a legal defense fund and even travelling to Vermont to directly protest Sanders. But now Addington says he is supporting Sanders in the Democratic presidential primary.

“Bernie made a big mistake, but this country has a lot bigger problems than what happened 20 years ago,” Addington said. “Not that that gives him a free pass, not that it makes him right, but we’ve moved on.”

Nuclear waste comes to Texas

Today, Texas is home to one of the nation’s few facilities that accept low-level nuclear waste. Since 2012, Waste Control Specialists in Andrews County has disposed of contaminated tools, building materials and protective clothing, among other items, from shuttered reactors and hospitals.

Environmentalists have closely scrutinized the site as it has broadened the scale of the waste it accepts, but the company insists that it is safe. The site has seen minor spills and leaks, according to federal regulators, but those had been localized and properly cleaned up.

Years before that waste arrived in Andrews County, it appeared destined for Sierra Blanca (population roughly 500), which sits about 90 miles southeast of El Paso. In 1998, the U.S. House — with Sanders’ support — approved the three-state compact, which then-President Bill Clinton signed into law, that paid wide-open Texas to take waste from the northeast. And years before, a Texas agency created to find a spot for such a facility chose Sierra Blanca, triggering environmental worries.

After Congress approved the compact, Texas environmental regulators rejected the Sierra Blanca proposal. The Andrews County site gained approval years later.

CNN’s Jake Tapper asked Sanders’ senior adviser Tad Devine on Tuesday about the controversy, noting that Clinton allies question how it squares with Sanders’ reputation for standing up for the disenfranchised.

“The only dump that's going on here is an oppo dump, okay, right before the primary,” Devine responded, laughing about the Clinton campaign's efforts to turn voters' heads just before the primaries. “Bernie Sanders has a very strong record of protecting people, standing up for people. The way he stands up for them is taking on powerful institutions and not taking money from them.”

Devine also pointed to Sanders’ opposition to fracking as evidence of his “extremely strong record on the environment.” Despite the Sierra Blanca episode, Sanders has attracted endorsements from many prominent environmentalists who praise his efforts to phase out nuclear power among other positions.

But when Devine served as a senior adviser on John Kerry’s 2004 presidential campaign, his candidate criticized both Howard Dean and George W. Bush for their support of the compact.

“He clearly reflected an insensitivity to that community,” Kerry said of Dean.

During the course of the current campaigns for president, Addington said he has noticed the issue resurfacing online, including references to his own accusations from the time that Sanders was committing environmental racism. But now that Clinton supporters are raising it during election season, he suspects “they're just doing it to gin up the minority vote.”

Bullard argued that it is “absolutely fair game” to resurface the criticism of Sanders’ stance on the long-settled issue during election season, describing it as part of the vetting process.

“It’s not something that should be glossed over,” Bullard said. “It was the wrong vote. It was wrong then and it’s wrong now. We need to look at his bona fides and see if he’s really who he claims to be.”

Sierra Blanca and the Democratic primary

According to a Texas Observer article from the time — provocatively headlined, "Sanders to Sierra Blanca: 'Drop Dead!'" —when activist Gary Oliver and others confronted Sanders to ask if he would at least visit Sierra Blanca, the representative offered a terse response.

“Absolutely not,” Sanders said. “I’m gonna be running for re-election in the state of Vermont.”

But now, much like Addington, Oliver is voting for Sanders in the Democratic presidential primary, even though he said he is still angry over the Vermont senator’s response to his protests.

“He’d be so much better than anybody else that I tend to put bygones aside,” Oliver said. “I’m not going to get a candidate I agree with all the way through. I’m not willing to send the country down the shithole just because I had a bad experience once with Bernie Sanders. But it’s still dirty.”

Among the most ardent political opponents to the plan were the late progressive U.S. Sens. Paul Wellstone of Minnesota and Ted Kennedy of Massachusetts. Wellstone, describing the intention to use Sierra Blanca as a site “blatant environmental racism,” proposed amendments to the bill that would allow the town’s residents to sue if discrimination influenced the decision to locate the facility there. Sanders supported passage without that amendment.

“Wellstone was a true progressive,” Bullard said. “So we were not just some wild-eyed radical environmental justice folks out there. We had real allies in Congress who said, 'this is wrong, this is unjust, this is unfair.' But Bernie was not one of them. In fact, he was the opposite.”

Former U.S. Rep. Silvestre Reyes, D-El Paso, also pushed back at the congressional level and remembers being frustrated with Sanders over the dispute, describing the Vermont senator’s views on it as “insanely callous.”

“It was the first time I’d come face to face with the arrogance that some of my colleagues called the ‘northeast attitude,’” Reyes said. “They were looking to dump nuclear waste and they didn’t care where it went as long as it didn’t affect the heavily populated areas where they came from. So when he says he cares for the little people, that’s contrary to my experience with him.”

Sanders' campaign manager Jeff Weaver said in a statement that the lack of safe options for disposing of nuclear waste is one of the reasons why Sanders has called for a moratorium on nuclear power. He also noted that the legislation before Congress did not specifically designate Sierra Blanca as the location for the nuclear waste dump.

"We were assured that regulators would not pick a site that would be harmful to the environment or local communities in Texas," Weaver said. "That’s exactly what happened. The good news is that the Sierra Blanca site was rejected and none of this nuclear waste was ever sent there. That was the right decision to make. There is no question that there was a real environmental justice aspect to the Sierra Blanca site."

Sanders maintains a connection to the nuclear waste agreement: Jane Sanders, the Vermont senator’s wife, now serves as an alternate commissioner for the Texas Low-Level Radioactive Waste Disposal Compact Commission.

But Addington pointed out that Sanders was far from the only Democrat who supported the plan and that even many Texas Democrats supported it. U.S. Reps. Sheila Jackson Lee, Eddie Bernice Johnson, and Gene Green — all supporters of Hillary Clinton — cosponsored the bill along with Sanders. While Addington said he took out ads against Sanders in a Burlington newspaper, he did the same against his own state representative at the time, Pete Gallego, in a Marfa newspaper, calling him “Plutonium Pete.”

"Everyone considers Sen. Sanders to be a progressive, so we did hold him accountable,” Addington said. “But Bernie was not alone, so why are they singling him out?"

But Bullard argues that nobody should get a pass for it.

“I don’t think that we should let the people who were making these decisions off the hook by spreading the blame,” Bullard said. “There’s no gray area. Everybody who pushed this proposal was condoning and acquiescing to environmental racism. Each person who was involved with this, their hands are dirty. And that absolutely includes Bernie Sanders.”

Jim Malewitz contributed to this report.