How do candidates reach potential voters?

The process
of reaching voters is a process that has two important steps.  The first step is identifying
which voters to contact while the second step is actually contacting those voters and getting
them to vote.

Perhaps the most important aspect of this process is
identifying the voters to contact.  Candidates do not want to waste their resources targeting
voters who are not likely to vote for them or who are guaranteed to vote for them.  Contacting
either would be a waste of time and resources.  Therefore, candidates use elaborate computer
models to determine which voters might vote for them and might also need to be encouraged to do
so.

Once they have figured this out, it is mostly just a matter of effort as
opposed to a matter of figuring things out.  The campaigns need teams of volunteers who will
contact as many potential voters as possible by phone.  For example, Mitt Romneys organization
was supposed to (but largely failed to due to technical problems) have people at polling places
finding out who had voted and calling potential voters who had yet to vote.

Thus, the process of contacting voters consists first of figuring out which voters to
contact and then of massive (largely volunteer) efforts to contact those voters and encourage
them to vote.