Anti-Trump intruders got into the Conservative Political Action Conference (CPAC) in Maryland and waved Russian flags emblazoned with the word Trump just before the president was due to speak.
The red, white and blue flags were seen being waved in the crowd before CPAC staff pounced and collected them. Jason Charter of Grassroots Campaigns said on Facebook that he was behind the prank, which was a dig at suspected links between Trump and Moscow.
"Had fun handing out Russian flags with the word Trump on them at CPAC," he said. "It was really fun calling Trump a fascist puppet to his face. Safe to say I won't be welcome back to CPAC anytime soon."
Charter, 22 and Ryan Clayton, 36, of Americans Take Action, told IBTimes UK that they were behind the stunt. Charter said that Clayton approached him with the idea last week. He replied: "We have to do it".
They said that only a small number of those in the audience seemed to notice that the flag was Russian. Charter was later thrown out of the conference for yelling during Trump's speech.
Outside the venue, Gaylord National Resort and Convention Center in National Harbour, Maryland, Charter said he was surprised when a number of young Republicans came up to him to express support.
They said they did not back the president and worried about allegations of his ties to Russia, he claimed.
The Trump administration's ties to Moscow have been a sore point in the US with allegations that senior Trump aides had contact with Russian officials during the election campaign. General Michael Flynn resigned as National Security Advisor after revelations that he called the Russian ambassador to talk about reducing Obama-led sanctions even before he had taken public office.
US intelligence agencies also released a report concluding that the highest levels of the Kremlin ordered interference in the November election in the hopes of aiding Trump's campaign.
One audience member who was handed a flag told the LA Times: "You have Secret Service out here, and I'd expect it to be fully screened. Thank God someone noticed."