Colin Delany describes how Square is being used in political fundraising here.

For political campaigns, Square has the potential to replace paper checks collected at fundraising events, easing transactions and simplifying reporting in the same way that online donations do. But note that we’re still talking about in-person fundraising, not something done remotely, so I suspect it’ll do more to streamline the process than to transform it. But it’s another step along the road to entirely wireless political fundraising, something that will likely be common within the next few years.

P.S.  Want to be Twitter’s first DC employee?  Colin’s post has the link.