Based on a survey of 2,010 US respondents, the Pew Internet Project found that about 1% of mobile phone owners had made a presidential campaign contribution through their mobile phones. This compares with 13% of all US adults who've made a contribution (using any method) to one of the presidential candidates in 2012.
By comparison, roughly 10% of US adults "have made a charitable donation of any kind using the text messaging feature on their cell phone." Among the 13% who've made a presidential campaign contribution, Pew says:
Regarding party affiliation and contributions, Pew found that "16% of Democrats and an identical number of Republicans have made a contribution to a presidential candidate . . ." However most Republicans make their contributions "offline," while Democrats "are much more likely" to make a digital contribution:
Earlier data from 2012, generated through surveys from UC Berkeley, Google and IPSOS, show that between 20% and 35% of US adults have made purchases (of one sort or another) on their mobile phones. It's not clear, however, whether these numbers include buying music or mobile apps -- probably yes.
Over time more and more people will simply use mobile devices to do what they would otherwise do on a PC, including making political contributions. In addition, people will become increasingly comfortable using stored credit card data to buy things with their phones.
To get more of the "lowdown" on mobile payments come see my panel at the Open Mobile Summit in San Francisco on November 7. The session is "Wallet wars: Mobile payments from theory to practice" and will feature speakers from PayPal, Google, HomeDepot and Visa.