Pew Research Center. October 28, 2014.

Voters are reporting roughly similar levels of contact from political campaigns and groups as four years ago, with one notable exception. The share of voters who say they have received a phone call about the election has fallen 12 points since mid-October 2010, from 59% to 47%. This decline has been driven by a fall in the percentage saying they have gotten pre-recorded campaign calls, or robo-calls. Other forms of campaign outreach appear to be close to levels measured in 2010. Nearly two-thirds of voters (65%) say they have gotten printed mail from candidates or political groups; 30% have gotten an email. Slightly fewer voters say they have been visited at home by someone than did so four years ago (14% now, 18% then). And the share of voters receiving text messages from candidates or political groups has remained flat (at 4%) since 2010. [Note: contains copyrighted material].

http://www.people-press.org/files/2014/10/10-28-14-Voter-Contact-release.pdf [PDF format, 16 pages].

The Brookings Institution. February 14, 2012.

In 2008, candidate Barack Obama pioneered several innovative applications of digital technology. With the help of the Internet, he raised $750 million. He made use of social media platforms such as Facebook and MySpace to identify and communicate with supporters around the country. Four years later, smartphones and handheld devices have proliferated and now outnumber desktop computers. Candidates, voters, activists, and reporters are using these vehicles for public outreach, fundraising, field organization, political persuasion, media coverage, and government accountability. Unlike 2008, where text messaging was the dominant feature of mobile campaign outreach, this year there has been a proliferation of mobile ads, video, web links, and apps. [Note: contains copyrighted material].

http://www.brookings.edu/~/media/Files/rc/papers/2012/0214_campaign_tech_west/0214_campaign_tech_west.pdf [PDF format, 10 pages].