A new ad circulating on social media hits MAGA right in the crotch!

The spot shows 2 utility workers griping about their taxes as they walk down a hallway, and then open a door to a computer server room -- but they find a GOP congressman on his knees "servicing" a rich campaign donor ... you get the picture.

The ad is funded by a Democratic Super PAC called the Progress Action Fund that's clearly no friend to MAGA. As one of the group's founders put it, "MAGA is going to HATE this ad. NASTY but accurate."

The founder says they made the graphic ad in order to reach 18-to-29-year-old males who might have supported Donald Trump. It's a key demographic that polls show is leaning Republican.

Important to note ... the ad and its message is not supported by or affiliated with any candidates.