I understand why Gingrich has agreed to debate. He's a very good debater -- and Trump "love[s]" him because Gingrich is a member of Trump's Florida golf club.
I also understand why Rick Santorum has agreed to appear. He's got nothing to lose -- and for some unfathomable reason, has never gotten his day in the sun as a "conservative alternative" even though, to my mind, he is far more intellectually and philosophically impressive than other former flavors of the month.
As for the rest of the GOP field, declining is the right thing to do, and here's hoping that Michele Bachmann and Rick Perry (the only other major candidates not yet committed) choose to do so. For Pete's sake, people -- we are trying to choose the leader of the free world here, not indulge in some reality-style spectacle that serves to enhance President Obama's stature by diminishing that of his challengers. Americans who believe that the presidency is worthy of some level of respect can't, in all consistency, support a competition for it that demeans the candidates, rather than elevating them.