Berelson et al 1954: Voting. A Study of Opinion Formation in a Presidential Campaign.

Berelson, Bernard, Paul F. Lazarsfeld, William N. McPhee 1954. Voting. A Study of Opinion Formation in a Presidential Campaign. Chicago: The University of Chicago Press.

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in a nutshell
Follow-up study to Lazarsfeld et al's groundbreaking 1944 "The People's Choice".

Gives evidence for that study's 'activation' mechanism: How social bonds make people change their voting decision. In other words, it gives evidence for 'the mobilizing force of social contact'. republicans, 88% vote Republican, if all three are Democrate, 15% vote Republican. counter to your family's: 25% change towards family's vote. if you are already in line, only 6% switch to other party. (when family undecided: 17% change).
 * 1) friends/coworkers: if all three closest friends/coworkers are
 * 1) family: if your vote intention a few months before the election runs