He doesn't do soundbites. In interviews his comments are thoughtful and often inconclusive rather than sharp and to-the-point. His dress sense is questionable.
He's every PR professional’s nightmare. But the reality is that Corbyn does his own kind of PR. And it seems to work.
He continues to behave more or less exactly as he has done as an MP for more than three decades: no glitzy press conferences, carefully crafted media appearances or expert makeover.
Where others may have sought out the limelight alongside the rich and famous, he's more likely to be found dealing with local problems at his constituency surgery.
The nagging question for many PR people is whether this turn of events signals the end of their usefulness as guardians of image and reputation, not just in politics, but in business and other walks of life.
Some argue that, largely because of the relentless exposure of the social media bypassing the traditional media, PR is dead.
The real point, however, underlined by the Corbyn phenomenon, is that it's evolved into something different.
PR must now teach people to be themselves.
Forget trying to appear bright-eyed and enthusiastic about every topic raised by your interviewee. People won't be fooled any more.
Wear the clothes you feel comfortable in, not those you think will impress the business community. Say what you really think.
It's all about authenticity. It’s a new type of PR, about appealing to real people in a way they understand and makes them respond.
Love him or loathe him, Corbyn is the best evidence right now that PR isn't dead, it's just changed.
Mark Whitehead is managing director of Headline Media