Famed Washington Post Watergate journalist Bob Woodward has called President Joe Biden's dismal showing in his debate against Donald Trump a "political hydrogen bomb."

Woodward expressed grave concern on Friday to MSNBC's Ari Melber over Biden's "awful" performance, and questioned how it went so horribly wrong despite extensive preparation.

He said Biden's debating was "so bad" that the American people have a right to know what was going on. 

"I sat there and watched it and I could not believe it. I said, not only is this a political hydrogen bomb for him and the Democratic Party [but], you know ... what happened? What happened?" he wondered. 

He added: "Look, let's step back. If a building blows up in downtown of some city, the story will be what happened, and then the story will be how did this happen, why did this happen? And that's where I'm very, very curious because this was a mega disaster."