[tehwalrus]

Politics is the art of persuading people they already agree with you. Subtler arguments are much better than brazen ones for doing this, and getting people to change their mind - and good politicians exploit this fact whenever they're in a setting that lets them.

24/7 media, and national coverage when somebody "flip-flops," might have contributed to politicians doing this less often, but I'm not sure.

And don't forget that a political debate isn't supposed to end with either politician changing their mind; it's supposed to end up with the spectators making up their mind about the politicians (which is why in those sorts of debates, you're supposed to use arguments that appeal mostly to your own supporters, assuming you have enough of them.)