As the race between Hillary Clinton and Bernie Sanders has become more intense, allegations of foul play, from misleading push polls to racist chants, have begun to fly from both sides. Some claims, however, are less credible than others.

In the latest accusation, National Nurses United, a 185,000-member union of nurses supporting Sanders, has said the Clinton campaign intentionally deceived caucus-goers on Saturday in Las Vegas by wearing T-shirts the same color as the signature nurses’ union scrubs.

According to RoseAnn DeMoro, the executive director of the union, Clinton volunteers put on red T-shirts in order to pose as the Sanders-supporting nurses and trick caucus-goers into believing the nurses actually support Clinton. After DeMoro tweeted a photo that she argued proved her case, the story went viral.

The kerfuffle angered many Sanders’ online supporters online. “What happened in Vegas will not stay in Vegas – return of Tammany Hall corruption,” DeMoro tweeted.

But there is little evidence to support her claims.

When DeMoro entered the caucus site at the New York-New York casino on Saturday morning, she said she spotted a group of Clinton volunteers who were all wearing bright red shirts—the same color as the nurses’ scrubs. One of the nurses called out that Clinton supporters were trying to trick caucus-goers. DeMoro tweeted her outrage. ”You don’t change your uniform on the day of the caucus,” she said later.

What DeMoro didn’t say is that many of the Clinton volunteers also wore blue-colored shirts.

On caucus day, the Clinton campaign set up its volunteers in two groups: the better-trained red shirts, who were meant to answer questions, and blue shirts, who played a supporting role. The red shirts said “Ask me questions about the caucus,” while the blue shirts simply said “I’m with her.” Both shirts were bilingual English and Spanish. The volunteers in blue shirts directed questions to the more knowledgeable volunteers in red shirts.

The patriotic-colored shirts were a tactic that made it easier for Nevadans to caucus, and perhaps more likely to commit to Clinton.

In the hours after the caucus, however, a National Nurses United spokesman suggested that the Clinton volunteers sought to conceal their deception from the media by putting on blue shirts. The spokesman said in a statement that when reporters walked in, the Clinton campaign volunteers quickly changed their attire.

“When our nurses walked into the room with cameras and a couple press the Clinton staffers ran over to the corner and quickly changed to blue shirts,” said spokesman Chuck Idelson. DeMoro later said the Clinton campaign had been “busted.”

But a TIME reporter was the only journalist who witnessed the initial exchange and the first to walk into the room. (A television reporter from a different outlet was on the same floor as the caucus site, but outside the caucus room.)

When the TIME reporter entered the room, there were several Clinton volunteers already dressed in blue. Others who slowly put on blue T-shirts appeared in no rush and did not seem to notice they were being observed. There was no evidence the Clinton volunteers were hiding their behavior.

A Clinton aide emphatically told TIME on Sunday there was no attempt to deceive caucus-goers.

DeMoro, who is highly critical of Clinton, said she expected questionable behavior.

“It was intentionally deceptive from our perspective. I expect the worst so I’m not surprised. I know machine politics. So I think it shocked our nurses more. I think our nurses are are in a state of shock,” DeMoro said. “I can only infer from what I saw. All I know is what I saw was deception.”

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