It is more than calling. It is using mathematics and data mining to profile the individual so one can map out identity, personality clusters to exploit with targeted messages via social media, direct contact, targeted mail etc.
It ensures the the electorate is engaged down to the individual level so on election day a GOTV ( get out the vote campaign) can be mobilized to push those people to the polls because they are motivated to do.
It needs special data mining skills and advance mathematics plus a marketing team who can custom design a message program to the individual level. A cattle farmer and a rice farmer have different interests even if they culturally identify with the same general things. A message to a Berbice cattle farmer up the Berbice river is also different from one on the coast. Up river the problem for example will be with vampire bats and flies depositing larve under the skin. On the coast this is not a problem but too much water or too little for extended periods is more the problem. A message addressing each of these farmers directly and speaking to their concerns means more to each than a general purpose message. These days the delivery can be over the internet, direct contact, phone call and other organizing memes.