Yeah.. I've been playing with it too. Not sure why it's not working. Normally Freze.It works great.
I've even tried tinkering with the URL, but that doesn't work.
Useful note... Anything after a '?' in a URL is just a variable and can be deleted. The same is the case with the '&' symbol.
So pretty much everything after the & can be stripped from the URL thus leaving just: https://www.mittromney.com/donate/fight-for-america