Of course...
...he did. He realized the WORSE possible outcome was for him to allow Obama to stand on the podium alone.
This on the other hand, could be the best outcome..."I tried to play the hero, but Obama was selfish, and wanted to focus on winning the election instead of saving the country, so I capitulated to mollify him, and to give the American people what they want - a debate."
It certainly will not make a wit of difference with his base, who will chose to not see it as the political election tactic it all was....so, what could it hurt?