It may need more shade, I know the Martha Washington does. It may also be the excessive moisture. Have you looked at the stem. Is it discolored just above the soil. If it is then it has Blackleg and it's a goner. It's more than likely though--if the leaves are crispty that it has blight. You can try treating it for that with a fungicide for blight.

I grow lots of Geraniums and I never had any luck with the Martha Washington either. I tried them twice and once it died and the other time it just didn't do well, so I gave them up as a lost cause. I think a lot of the fancier Geraniums are just not as hardy as the regular zonals.

Good luck