The video quickly went viral on social media, sparking the trending hashtag #Fartgate.
Many social media users were adamant Mr Swalwell had accidentally let one rip on air.
"Eric Swalwell appears to drop a massive fart during live on television. Turn the sound on, this is real," one Twitter user said.
"I heard this live and thought it was my dog. It was not," another wrote.
Another added: "It is real you can tell the pause he takes to push it out."
However, other people thought it could have been the host Chris Matthews or another person in the studio.
"Maybe it was Chris Matthews?! Everyone is so quick to blame Eric, it's possible it could of been Chris," another person said.
One added it could have been the person holding the microphone.
Mr Swalwell has denied all allegations he farted on air, telling BuzzFeed journalist Addy Baird he didn't even hear it.
"It was not me!!! And I didn't hear it when I was speaking," he said in a text.
When the reporter pointed out it looked like he was stifling a laugh in the video he said he definitely "did not hear it".
However he did admit the situation was funny.
Since the video went viral, some people have claimed the noise wasn't a fart at all.
One person suggested it was the sound of a mobile phone vibrating on a table.
Hardball has also addressed the incident on their official Twitter page, claiming it was the sound of a mug scraping along a table.